When Des finds himself in a very bizarre and compromising position, the Doyle clan works overtime to get him off the hook; Jake meets someone who has been complicating Allison's life; Tinny and Des start coming to terms with their feelings for each other.
The Doyles reluctantly take on a case from dodgy Martin Poole when he promises them a big payday; Jake and Allison encounter friction when their professional lives impose on their personal relationship; Jake gets an interesting job offer from an unlikely source.
Guest stars: Nicholas Campbell (Martin Poole), Greg Malone (Finn).
Jake dodges his ex-wife Nikki while wooing his ex-girlfriend Leslie – who'll have none of it. It's a trip down memory lane as the Doyles investigate the murder of an old client.
But when the body count rises, Jake starts to question the whole case.
Jake plays prisoner when he goes "inside" to find out the location of some stolen diamonds from a gang of incarcerated criminals; Mal finds out that Rose has been keeping a big secret from him; Tinny's money-making scheme starts to take root.
Guest stars: Gordon Pinsent (Maurice Becker), Alan Doyle (Wolf Redmond), Mayko Nguyen (Dr. The Doyles are employed to help a comedian on the edge of a comeback find a dangerous stalker; Leslie defines the boundaries for the men in her life, including Jake; Allison reveals something to Jake that could be a game-changer. It's matrimony – Doyle style – as Jake and Mal are tasked with finding the person responsible for sabotaging an upcoming wedding; Mal and Rose fix a bump in the road in their relationship as Jake and Allison hit a stride in theirs; Des comes to Tinny's rescue but ends up exploding her plans in the process.
Jake and Mal investigate a hit-and-run and encounter a slippery criminal couple; Rose has a run-in with familiar ghosts from her past; Des discovers that Tinny's trip to London didn't go as expected. Novelist Garrison Steele returns, hiring the Doyles to track down the love of his life.
On the homefront, the Doyles get a new houseguest who's not planning on leaving any time soon.
The Doyles start trailing a potentially cheating husband to find he deeply loves his wife but is in deep trouble with some menacing criminals and smugglers; as Nikki moves forward with her new beau, Jake and Leslie take it to the next level.
Guest stars: Gordon Pinsent (Maurice Becker), Mark Critch (Ned Bishop).
The season finale aired on April 7, 2010 and drew 1,120,000 viewers.