Psycho II ending explained (spoilers)

[carla]

Mary is really the daughter of Sam Loomis and Lila Crane from the first Psycho. Sam is dead, but Lila intends to make Norman go insane again by dressing up as his mother, and by calling him and pretending to be his mother. Eventually Norman does go insane again and kills Lila. Mary (not knowing what's happened to Lila) tries to dress up as his mother and convince him that it's all a lie, but Norman forces her down to the coal cellar, where Mary discovers Lila's body. Mary threatens to kill Norman, but as she does, the police break in and shoot her. Mary and Lila end up being blamed for the murders and Norman is set free. Later on he's visited by a woman called Miss Spool, the sister of Norma Bates, who claims to be Norman's real mother. He kills her with a shovel and takes her up to his mother's room, where she becomes his new Mother.