Farscape/Recap/S04 E21 Were So Screwed La Bomba

Season 4, Episode 21:

We're So Screwed, part 3: La Bomba
Crichton manages to get his vitals -- and the nuke -- under control as Staleek and the Scarrans show up, having captured the rest of the crew and set up defences to ensure ships can't leave Katratzi, meaning that the crew would've been killed anyway had they tried to escape. They manage to keep their cover intact, but Staleek and Ahkna are onto their scheme.

In private, Crichton questions Scorpius about what's going on. It's revealed that Scorpius actually possesses no wormhole knowledge beyond what he learned on the now-defunct Gammak Project; Harvey was lying in order to convince Crichton to return for Scorpius, as per his reprogramming. However, the reason why Scorpius kept Crichton on the base is because he wants the help of Moya's crew in accomplishing an objective he believes is, at that point in time, even more important than wormhole technology: Crystherium, the flower that the Scarrans are growing in their high-security cavern beneath Katratzi. Scarrans only evolved to their current level of intelligence by eating the flower, which affects their brain chemistry, and they must continue to eat the flower regularly in order to keep their higher brain functions. The flower can only be grown under rare conditions and the Scarran Empire can only expand from locations where the flower grows. Scorpius wants to destroy the crystherium cavern beneath Katratzi, which would be a huge setback to the Scarran invasion of the galaxy; he's been searching for crystherium caverns for cycles, and the reason why he first captured and interrogated Stark is because the Banik slave used to work for the Scarrans and knew the location of Katratzi's crystherium.

The crew agree to help Scorpius destroy the crystherium. While the others set up their plan to get access to the cavern, Aeryn visits Grayza's command carrier to get a Peacekeeper medical procedure performed. The crew plan to use the drill on one of the elevators to tunnel down into the cavern. To get the access codes, Scorpius advices that they find Stark -- the real Stark, not the bioloid who was torturing him as part of Staleek's ruse to convince everyone that Scorpius wasn't a Scarran spy (which is revealed to have been another deception of Scorpius' part, as he only pretended to work for Staleek so that he could search for crystherium locations). It's at this point that all hell breaks loose (again): the Scarrans are able to remotely deactivate Crichton's bomb and the Charrids come after Moya's crew. While Rygel and Noranti look for the real Stark in the bioloid duplicator, Sikozu manages to get the drill working and she, Crichton, Aeryn, Scorpius, D'Argo and Chiana descend into the crystherium cavern. Once Rygel and Noranti have Stark, D'Argo remote-activates Lo'La and they use her to escape the base. At the same time, Grayza's command carrier detects weapons fire on the base and intercepts orders calling for Crichton's death. Realising that the peace negotiations have failed, Grayza orders the carrier to battle stations and prepares to go out fighting the Katratzi base defences; Captain Braca removes Grayza from command, takes control of the carrier and orders a full retreat.

Once the elevator/drill has reached the cavern, Scorpius attempts to destroy the main crystherium flower that keeps the other alive, but it's protected by an energy shield that the group's weapons can't penetrate -- nor can their weapons harm the squad of Scarrans descending towards the cavern. Sikozu chooses this moment to reveal not only her origins as a bioloid, but an extra ability that a regular organic being couldn't possess: pyrokineses. When the Scarrans arrive, Sikozu unleashes a blast of fire that destroys them. The group try to escape the cavern using their elevator/drill, but they have to go in the opposite direction or risk capture. With Charrids and Scarrans closing in on their location, Crichton plays his final ace: he reactivates the nuke and drops it down the shaft created by their elevator/drill. It lands in the crystherium cavern, at the feet of another Scarran squad, and they barely get a chance to read the words "Hi There" before it explodes, destroying all the crystherium, killing most of the Charrids and Scarrans and almost completely annihilating the base. The crew are relatively safe inside the elevator/drill and once the debris settles, they are able to rendezvous with Lo'La and get back to Moya.

Once the crew is safe and free, most of them are overjoyed at their escape and keen to celebrate, but Crichton is overwhelmed and driven to near-catatonic by his actions.