In April 2019, a seemingly tame beluga whale approaches a Norwegian fishing boat seeking help. It is wearing a harness fitted with a camera mount. When the words 'Equipment St Petersburg' are discovered printed on the buckle, speculation breaks out that he has been engaged in some kind of sinister undercover activity. This documentary explores the mystery of the strange whale and asks where he came from, who trained him and why, and what he was doing in a critically important part of the Arctic, close to Russian waters. With exclusive interviews and access to unseen footage, the film explores the secret world of marine mammal training and international espionage, and sheds new light on the true identity of Hvaldimir, the 'Spy Whale'.