Matlock agrees to defend psychiatrist Lucas Forbes when he's arrested for killing Adam Whitley, the husband of one of his patients whom Lucas was reportedly having an affair with, according to the woman's diary. Matlock soon realises that Erin Whitley has a host of deep-rooted psychiatric problems. After a few chance meetings with a woman named Shannon, Matlock is shocked to realise the extent of the connection between Erin and Shannon.