A mysterious injured man undergoes an astonishing transformation.
The Enterprise rescues a severely injured humanoid from a crashed escape pod. Dr. Crusher treats him, and he recovers quickly, with no memory of who he is. The crew calls him John Doe. As he heals, he exhibits curious abilities, and he forms a bond with Dr. Crusher.
He also begins to undergo a strange physical transformation, and a group of aliens arrive who are hunting him, believing that he is a criminal. The episode explores the ideas of identity and evolution and has an affecting story of a being on the verge of a great change. The ending, with its theme of transcendence and forgiveness, is a memorable and quietly moving moment.