After Greg Winchester gives the detective duo a ring with a mermaid on to give to his ex wife before he dies in a "on set accident," Robin begins to ponder about the link between the people on the list. Having noticed the tattoo on the vicar's hand, plus the fact that the first victim worked in the merchant navy, the duo discover a connection with the S.S. Mermaid, a ship which sank in 1953. Realizing that Winchester's ex wife Sarah Bedford is in grave danger being next on the list, they head out to Tunisia to find her. But with gangster Joe Galliano also on their trail and out for blood, it proves a very dangerous place for all concerned.