The Key of the Door - S1.E12

Winter 1908: Elizabeth befriends a bunch of Bohemian-types, but is drawn to two in particular: Evelyn Larkin, a radical Socialist extremist, and her lover, Lawrence Kirbridge, a handsome, free-spirited poet.

On the eve of her 21st birthday, with her parents out of town, Lizzy invites the entire group to Eaton Place, and is humiliated when the Bellamys return home unexpectedly and throw everyone out. Anxious to prove she's nothing like her parents, Lizzy is compelled to do something extreme, leading to a falling out with her parents and a harsh discovery about Evelyn.