The arrival of Miss Lambe's forbidden love causes Charlotte to question her opinion of Sidney. Meanwhile, Clara witnesses a moment between Esther and Sir Edward that raises her suspicions about their relationship, with devastating consequences for Esther.

Charlotte and Sidney are at loggerheads but must work together to try and rescue Miss Lambe. Tom tries to save Sanditon and his marriage, whilst Edward and Clara enter into a scandalous pact to try and finally win Lady Denham's inheritance.