Conscience Makes You Go Back

Paul: You can't just walk away.
Jarvis: You did.
Paul: (sighs) How did I end up with Jiminy Cricket? (turns the car around)

—Necessary Roughness

Someone is about to walk away from those in need, but then have a moment when they realize it's wrong. So they go back and help.

Say our hero, or lancer, Bob isn't interested in helping Alice. Either he did his job already, or he owes nothing to her. It's not his problem, and he's Not in This For Your Revolution. So Bob just walks off... And then about thirty seconds to a few minutes later, Bob's face shows he can't do this. He has to go back and help. He's annoyed, or even angry, but he does go back.

This can overlap with Ten-Minute Retirement, or Changed My Mind, Kid. The key is that we have to specifically see these characters stopping on their way, and realizing they have to do this.

Even villains can do this, because of course Even Evil Has Standards. When forced to own up to why they did it, the character may gripe that Being Good Sucks.

Examples of Conscience Makes You Go Back include:

Comic Books

In the Carl Barks story "The Horseradish Story," Scrooge McDuck does this when he has to Save the Villain: as the swindler Chisel McSue dangles helplessly from the side of Scrooge's raft, Scrooge spends three panels ranting about how he has no reason to save the guy who's trying to take all of his money, and if he doesn't save McSue, all his troubles will be over... Then, at the last second, he rushes to the rescue.

Scrooge: Oh, phooey! I'm a soft old fool! I can't let the rat down!

Film

In the first X-Men movie, Logan leaves Rogue stranded by the road, and then realizes he can't just leave her out there.
Ray Liotta in Cop Land does this, and then practically screams at his conscience over knowing he has to go back and help.
In Chicken Run, Rocky leaves the other chickens to fend for themselves, but turns back after seeing a billboard for Mrs. Tweedy's Homemade Chicken Pies.
In Pulp Fiction: Butch, a boxer on the run from gangster Marcellus Wallace for failing to throw a fight for him, is captured alongside said enemy by a store owner and his hick cop buddy. While the sickos rape and beat Marcellus in the next room, Butch escapes his bonds and makes for the door, but stops when he hears Marcellus screaming. After a brief pause, he reluctantly searches for a weapon, picking a katana, and heads back downstairs, where he saves his enemy and his conscience.
In Black Dynamite, Black Dynamite is leaving the White House when he decides he just has to go apologize to first lady Patricia Nixon for hitting her. Even though she was shooting at him. She really thinks he was perfectly justified but appreciates the apology anyway.
In Pirates of the Caribbean: Dead Man's Chest captain Jack Sparrow abandons his ship and his crew to the Kraken's mercy but then returns in the crucial moment and saves them all.
In No Country for Old Men, Llewelyn sees the aftermath of a firefight, and just takes whatever's not nailed down, ignoring the survivor begging for water and even leaving the car door open against his wishes out of spite. That night (when the man couldn't possibly have been alive), he feels guilty and brings a gallon of water to the site; things kind of go downhill from there.
In Harry Potter and the Goblet of Fire, Harry almost allows Cedric to be devoured by the maze during the third task, choosing instead to run to the Goblet while he has the chance (due, in part, to the maze's quasi-demonic influence over whoever enters). He ultimately decides to run back to pull Cedric free.
In District 9, protagonist Wikus van de Merwe comandeers an alien mech, giving him a small chance of escaping his mercenary pursuers. He gladly abandons his once-companion, the alien, Christopher and runs for it...and then Wikus overhears the mercenaries' plan to execute Christopher. What follows is awesome.
In An American Werewolf in London, David and Jack are walking on the road in the middle of the night when suddenly Jack gets attacked by a large werewolf. David runs away in fear. Realizing that he can't leave his friend to die, he decides to go back and help him. It doesn't go quite well for either of them...
At the end of The Wild Bunch the remaining bandits failed to save their friend from the local warlord and are now getting ready to leave with their money. However, they realize that their conscience won't allow them to let the warlord get away with murdering their friend like this and their go back for a final Roaring Rampage of Revenge.
Lampshaded in the film Necessary Roughness.
One of the staff memeber briefly does this in Titanic when Jack and Rose come to a locked stairwell and see him on the other side trying to head to the upper deck. He nearly leaves them there but ultimately turns back to try and unlock the door. However he drops the keys in the quickly flooding water, give a quick apology and leaves them. Forcing the two to search for the keys and unlock the door themselves.
At the climax of Happy New Year, after the heist is successfully completed, Mohini declines to escape with the rest of the band and decides to get back to the dance competition finale, fully conscious that she risk being arrested, because she did work hard on her dancing and because she cannot disappoint the fans they gained at the event. Rohan decides to accompany her, because his conscience won't leave him in peace if she has to confront either the public or Grover alone. When Charlie tries to convince the rest to leave them behind, the group are so appalled by his callousness they decide to go back too. In the end, even Charlie decided to go back and appear in their dance number at the very last moment. And good thing he does so, because the full band reappearing for the finale trows away Grover's accusation against them.
Quigley Down Under; after it becomes obvious that Quigley will not be an accomplice to murder, Marston tells his flunkies to bring him and Cora out into the desert to kill them. Quigley turns the tables on them, but that doesn't change the situation - they're lost, and in the middle of nowhere. Quigley briefly considers abandoning Cora - after all, she hasn't helped him much at all and would only slow him down - but chivalry wins out and he manages to carry her until a group of Aborigines find them.
In Twins, Julius makes Vincent grow a conscience, which irritates Vincent to no end -- and forces him to return to Julius's side when Julius is in danger, despite Vincent preferring to run off.
In The Iron Giant, Hogart sees the Giant get caught in some electrical wires, roaring as electricity runs through him. At first Hogart runs away, but then senses that somehow this metal thing from outer space is suffering, so he runs back and turns off the power station, saving him.
In The Emperor's New Groove, Pacha warns Kuzco not to go out into the jungle alone. Kuzco ignores him and Pacha has every intention to let him get killed, since that would solve all his problems once and for all. He starts walking away, but can't bring himself to continue and goes after Kuzco.
In Ratatouille, Colette returns to the restaurant to help Linguini and Remy after remembering her idol's Gusteau's motto: "Anyone can cook".

Literature

Huckleberry Finn's line "I'll go to hell" counts, since he was prepared to betray Jim and then changed his mind. An unusual case in that due to Values Dissonance his subjetive thought was more like "I Have To Do The Wrong Thing".
Discworld:
- In Sourcery, Rincewind has this, when what he really wants to do, and really thinks that he should do, is flee for his life, but his conscience forces him to try to stop the all-powerful wizard Coin from destroying the universe. He even argues against his conscience. End result: Rincewind goes up against Coin with a brick in a sock. and inadvertently succeeds in stopping the destruction of the universe by accidentally inducing a Heel Face Turn in Coin.
- Also happens in The Light Fantastic; Twoflower declares he's going to go back to make sure Cohen's all right, and Rincewind says he's not going along. Cut scene to the two of them tied up, having been ambushed on the way back. In this case it was a mixture of conscience and The Luggage.

Twoflower: I thought you'd come back.
Rincewind: I don't want to talk about it.

In The Stormlight Archive Highprince Sadeas betrays Dalinar and leaves him and his army to be slaughtered by a vastly larger number of Parshendi. Kaladin, who originally wants to use this as a way to escape from Sadeas ends up deciding (with encouragement from Syl) to return with the bridge and save Dalinar and his men because somebody has to do the right thing.

Live-Action TV

In the Doctor Who episode "The Waters of Mars", the Doctor is leaving Bowie Base One and its crew to their unalterable fates. He can hear their frantic efforts to survive turn to failure as more and more of them fall to the waterborne virus, culminating in the self-destruct of their shuttle. Then he remembers his own words: "I'm not just a Time Lord, I'm the last of the Time Lords". And he returns to save those he can.
Lennier in Babylon 5 has had a serious crush on Delenn the entire series, but she married John Sheridan. Near the end of the series, Sheridan gets trapped in a sealed hallway filling with poisonous gas, and Lennier who could easily save him (and the unconscious Ranger that Sheridan was trying to save). Instead, he leaves so the gas can Murder the Hypotenuse. However, he says to himself that he can't go through with it. Sheridan saves himself, and upon seeing this, Lennier flees in shame.
One episode of the early 1960s detective show Checkmate had "Jocko" Townsend planning to murder Professor Hyatt, whose psychological assessment of him ten years before had resulted in Jocko spending those ten years in prison. At the end, he's locked Hyatt and two other detectives in a booby-trapped room, cheerfully strolls back to his hotel ... and then exclaims, "I can't do it!" and races back to let them out. Hyatt had actually managed to disarm the bomb before Jocko even left -- but giving Jocko the chance to come back as he did was part of proving that he didn't have to be the violent thug he considered himself.

New Media

Vita from Vigor Mortis let Grig beat his son because she didn't want anything unusual to be noticed. Then she felt bad about it and stopped it.

Video Games

In Dragon Age II, if you manage to get Isabella's friendship/rivalry meter high enough, she will return the Qunari relic to the Arishok rather than save her own skin.
In Corpse Party, Ayumi and Yoshiki are returned to the classroom by one of the ghost children as thanks for returning her tongue. Ayumi wants to go back and save their surviving friends. Yoshiki, if you choose to object (or allow Yuka to be caught by Kizami) will do so and Ayumi will return alone after an argument. Yoshiki, however, is reminded of how much his friends mean to him and begs the ghost girl to send him back. It still leads to a Wrong End, though.
In Solatorobo, when Elh is captured by the Kurvasz, Red seriously considers leaving and declaring the whole issue Someone Else's Problem. Especially since Elh did betray them and tried to sacrifice him in the Rite of Forfeit. Chocolat agrees with him initially, but it's all a ploy to get him to realize that they should turn around and go rescue Elh.
In Scratches, the protagonist, Michael, is about to leave the haunted mansion but decides to stay until he purges the curse of the mansion, fearing that something terrible might happen to someone in the future if he leaves just like that.
In Ib, Mary does this in the ending "Welcome to the World of Guertena". If Ib has formed a strong bond with Mary, then even if Ib collapses from despair in the doll room, Mary will come back to stay with her, abandoning her dream of escaping to the real world. Possibly Mary's most selfless action in the entire game.
Many fans of Batman: Arkham City feel that the Bad Ending (which happens if Catwoman chickens out and leaves Batman to his fate) is, in effect, Catwoman weighing the consequences of doing so and changing her mind. The fact that the credits reverse themselves and let the player rethink that decision lends credence to this theory.
Paper Mario: The Thousand-Year Door; when Mario and Vivian manage to correctly guess that name of the one who has stolen Mario's name is "Dooplis", Vivian also realizes she's been working with Mario - who's supposed to be her enemy. At first, she flees, not knowing what to do, but after Mario fights the battle alone for a few rounds, she comes back, fully completing her Heel Face Turn.
Villainous example in the Ratchet & Clank series. Lawrence, Doctor Nefarious' dry-witted assistant, has a Screw This, I'm Outta Here moment in every game, but to date he's always come back to save his boss.

Web Comics

Stunt does this in a recent strip of Dominic Deegan when he briefly considers not saving someone who he hates for being a ~~slaver~~ poacher and, possibly worse, a woman.
In The Order of the Stick, team leader Roy has a crisis of conscience and realizes that he can't abandon a helpless innocent and still call himself Lawful Good.
Miss Cummings from Birthday Gift comes back for Miss Cox, after initially declined because she wants to "stick it to the men". It was a trap.

Western Animation

Subverted in the Looney Tunes short "Bugs Bunny Rides Again". Bugs has tricked Yosemite Sam into walking off a cliff. Suddenly he runs down to the bottom and puts down a mattress, explaining to the audience, "Sometimes me conscience kinda bothers me... but not this time!", and pulls away the mattress at the last minute.
- Bugs plays it straight in "Frigid Hare", when a penguin he's been trying to get rid of gets captured by an Eskimo. At first he goes "Oh, well. I'm not my penguin's keeper" and sets back to his hole. Moments later, he pops back up and goes back to save him, but not before he tries to explain himself to the audience.
Futurama: Fry is about to leave Leela, who is chasing him, trapped in a cryogenic chamber for a thousand years. Conscience gets the better of him, and he changes it to five minutes: 'you owe me!'
In Aladin: The Return of Jafar, Iago saved the good guys from Jafar. So he's done now. No, seriously, he doesn't owe them anything else, so he is not going to risk his life trying to defeat Jafar. Then he does.
In an episode of the The Legend of Zelda animated cartoon, Link feels spurned and rejected by Zelda in favor of White Prince. Link leaves the castle but hears Zelda's screams for help after the Prince refuses to help her. Link thinks to himself before turning back to aid her saying "Bah, I'm such a sucker".
In the DuckTales episode "The Golden Fleecing", Scrooge McDuck almost abandons Launchpad in danger over the Golden Fleece, but the friend's scream for help brings Scrooge to his senses.
In Phineas and Ferb, after Perry foils yet another of Doofenshmirtz's plans, he is about to walk off, but then he realizes he left Doof in a position that would humiliate both him and his daughter. Perry goes back to fix it.
In the Teen Titans episode "X", Red X at first has no desire to help Robin rescue the team from Professor Chang, stating he's Only in It For the Money and doesn't like playing the hero. Later, however, he changes his mind and pulls a Big Damn Heroes:

Robin (jovial tone): I thought you didn't like playing the hero!
Red X: Doesn't mean I don't know how.