Character Arc
DS Kirsten Longacre is Amy's partner and lifeline, working the case from shore while her colleague is sealed inside the submarine and out of reach. Sharp, loyal, and relentless, she chases the leads the Navy would prefer to bury, following a paper trail of activists, intelligence officers, and inconvenient deaths. Her investigation steadily reveals that the killing aboard ship is only one knot in a far larger conspiracy.
Kirsten's connection to Amy is more than professional, and the case forces unresolved history between them back to the surface. As she pulls at the threads on land, she finds herself watched, warned off, and increasingly in danger, yet she refuses to abandon Amy or the truth. Her grounded, methodical work counterbalances the high tension below the waterline.
In series two, Kirsten remains a steadfast presence in Amy's life, supporting her through a new and equally perilous inquiry. Their partnership has matured into something deeper and more settled, even as fresh threats test it. She continues to embody the show's quieter heroism: the patient, dangerous work of following evidence wherever it leads.