Recovering addict Tommy Jarret rented a chalet to check on reports of a sea monster near the dour village of Drim. But when he turns up dead, apparently of a drug overdose, Lochdubh constable Hamish Macbeth finds the lad's demise to be particularly fishy - and not of the local salmon variety. Deciding to pose undercover, Hamish infiltrates the illicit drug trade in nearby Strathbane. But his daft scheme springs a leak when Hamish is teamed with a tough Glasgow detective inspector named Olivia Chater, aka "concrete knickers." Now in a charade that puts the intractable Highlander in a designer suit among the sharks of the underworld, Hamish's craving for justice will be tempered by a dependence on Olivia. For the lanky lawman, it's time to sink or swim - and it would be equally dangerous to flounder... or fall in love.