Gwinny Tuffel is preparing for her first acting role in a decade in the West End, but she is dog-sitting on the side to keep the wolf from the door. So, when ageing rock star Crash Double needs help with his Border Collie, she jumps at the chance. After all, looking after the charming Ace on Crash's Little Venice houseboat shouldn't be an onerous task. But that's before the singer's dead body surfaces during the annual Canal Carnival festivities.

While the police dismiss the death as an accident, Gwinny suspects murder most foul. With a medley of suspects and some far-fetched motives to make heads or tails of, it is up to Gwinny, with Ace's on-the-ground knowledge, to make sure the killer faces the music.