Echo becomes a backup singer to watch out for a female singing sensation with a very overzealous fan. Agent Ballard's investigation takes a turn for the worse.

When Adelle’s wealthy friend is murdered, Adelle imprints Echo with the woman’s memories and personality to solve the case. Ballard looks into Mellie’s past, and Topher secretly programs Sierra for an engagement.

Sierra is forced to face her past as her connection to the Rossum Corporation leads to obsession and murder.

After her entanglements with Senator Perrin and the DC Dollhouse, Echo finds herself out in the world-at-large as she struggles to control her multiple memory downloads. Topher discovers the dangers of science that will have devastating effects on the future, while Adelle engages in a power struggle with Harding.

When Adelle, Boyd, and the rest of the Dollhouse fear that Echo's uncontrollable mind imprints are making her a danger to their goals, they send her to "the Attic" where Echo is forced to face her worst nightmare in order to survive.

In the year 2020, Echo and her surviving Dollhouse crew attempt to restore order to a devastating future world before mankind is eliminated.