With Curtis in the hospital and Hibiscus recovering from the attack on the Gully, Millie throws herself into her work. Initially suspicious of U.K. Detective Luke Holborn, Millie is compelled to team up with him when Janet's case leads to a disturbing discovery.

Millie reluctantly agrees to work with Holborn in the short term. Meanwhile, Hibiscus and Millie find a new balance in their relationship, and Curtis contemplates a change. Then, when Millie and Holborn make a breakthrough, Millie finds herself on a dangerous path.

Not knowing whom to trust, Millie goes rogue to get to the bottom of the Somervilles' criminal enterprise before Holborn can interfere. When Janet makes an unexpected decision, Millie must take extreme measures to protect the ones she loves and to find Romeo before it's too late.

In Kingston, Curtis faces the consequences of Millie's actions and must decide what matters most. Meanwhile, an undercover Millie arrives back in London. With few friends and scant resources, she must find and save Romeo before the mysterious "Lindo" can stop her.