Inspector Rivera's former girlfriend, Sara, rings him seeking help. She's seen her partner Francesco hanging from a tree in her garden. But when Rivera arrives, the body isn't there, and his team begins to raise doubts about Sara's state of mind. A reappearance by Francesco causes Sara to question her own sanity.

Valentina Cavalli is a key witness in a conspiracy trial against a bank. On the day she is due to appear in court to testify, a gas explosion occurs in the flat next door to hers. The gas mains have been tampered with and it's obvious that someone wants her dead. But who is behind the attack? Inspector Rivera and Rex investigate.