In the exciting final installment of the Lost Voices trilogy, mermaid Luce swims to the San Francisco Bay where she finds a group of renegade mermaids who become an army under her leadership when war breaks out between humans and mermaids.

Mermaids have been sinking ships and drowning humans for centuries, and now the government is determined to put an end to the mermaid problem—by slaughtering them all. Luce, a mermaid with exceptionally threatening abilities, becomes their number-one target, hunted as she flees down the coast toward San Francisco. There she finds hundreds of mermaids living in exile under the docks of the bay. They are the Twice Lost: once-human girls lost first when a trauma turned them into mermaids and lost a second time when they broke mermaid law and were rejected by their tribes. Luce is stunned when they elect her as their leader. But she won't be their queen. She'll be their general. And they will become the Twice Lost Army—because this is war.