Star Trek VI: The Undiscovered Country/WMG

Colonel West was actually Odo, on an early mission from the Founders to destabilize the Alpha and Beta Quadrants.

 * He must have suffered some long-term memory loss after this movie to make him forget who he was and why he was there. As for him getting shot out the window and lying in a puddle of blood, it's all part of his scheme to keep his cover.
 * Then how come his blood didn't turn to changeling-fluid when Colonel Worf rubbed it between his fingers?
 * Odo's day-to-day appearance was based on the Bajoran doctor who studied him. And as Odo himself pointed out to Kira, it's just a shape he assumes, not part of his identity the way it is with us solids. There'd be no reason for him to resume it for a completely different identity decades later.
 * Ye gads, you mean the Bajorans were in on the plot too?!
 * How about Martia as a Dominion spy? We know she's a shapeshifter.