The question of how gender and trauma may impact one another is explored through detailed clinical material from the author’s work with a patient contemplating, and then beginning, a transition from female to male. The author explores what happens when a mind is colonized rather than mentalized. The term colonize is used to describe the unconscious use of a child’s mind to store unprocessed trauma from an earlier generation. The author describes destabilizing feelings of uncertainty, shame, and anxiety in both patient and analyst at various points in the treatment.