Dexter (2006)

S7E5 Swim Deep

Title: Dive Below Plot: As Dexter investigates the mysterious murder that occurred on his vessel, he finds himself in a dangerous game of cat and mouse with the vengeful Isaak. Meanwhile, Hannah McKay, the captivating ex-partner of Wayne Randall, surfaces with new insights into the Randall case, but Dexter soon realizes she harbors a hidden agenda of her own.