Gemma Wyatt, a wildlife ranger, is found dead off the coast of the bird sanctuary where she spent the night alone whilst colleagues celebrated her boss Sophia's leaving do on shore. Estranged sister Alice accuses Gemma's boatman boyfriend Ryan of trying to force her to sell the family farm but he claims it was for Alice's own good. Vera establishes that Gemma was killed before the others left for the mainland, making them all suspects, and also locates a couple who blame Gemma for their son's death on the island some years earlier. Then Alice hits Vera with a surprise revelation, leading to evidence of Gemma's infidelity and involvement in a blackmail plot before the killer is revealed.