In "Let's Kill Hitler", the Doctor encounters a younger iteration of River and learns she has been conditioned by the Silence to assassinate him and nearly succeeds using a kiss of poisoned lipstick before Amy convinces her to save his life instead.
In "Let's Kill Hitler", the Doctor encounters a younger iteration of River and learns she has been conditioned by the Silence, explained to be a religious order, to assassinate him. She nearly succeeds using a kiss of poisoned lipstick before Amy convinces her to save his life instead.