Michael C Hall is back for the third season of Dexter. But everyone's favourite serial killer isn't the only one in the Miami Metro police wielding a knife

What does Lt Maria Laguerta dream of when she’s sleeping in her coffin? Presumably new ways to cling to her job by her sharp and bloody claws.

Laguerta (Lauren Velez) scrambled over former partner Doakes to the top job by taking credit for his arrests. When she lost it through incompetence, she befriended her replacement Lt Esme Pasquale, while engineering her resignation by secretly shagging Esme’s boyfriend and turning her into a paranoid wreck.

In the opening episode of the third series of Dexter (FX, 10pm Fridays) Laguerta returned to her favourite sport of persecuting Dexter’s feisty, funny, foul-mouthed sister Deb precisely because she’s a good cop and Laguerta’s a very mediocre one indeed.

Deb (Jennifer Carpenter) discovered that murder victim Oscar Prado wasn’t the upstanding member of society he seemed. Oscar, who died in a knife fight at a drug dealer’s house, was believed to have been trying to stop the dealer selling to kids.

But in Deb’s words, delivered at full volume to her stunned colleagues, he was there because: ‘He was a f****** junkie!’

Unfortunately Oscar’s grieving brother, State Prosecutor Miguel Prado (Jimmy Smits), happened to be standing right behind Deb at the time, giving Laguerta an excuse to have Deb removed from the case.

Little do they know that Oscar wasn’t killed by dealer Freebo, but by Dexter (Michael C Hall), who planned to add Freebo to his collection of blood slides but got the wrong man by mistake.

Dexter is breaking free of the influence of his late father Harry, who channelled his psychopathic stepson’s ‘special talent’ into a force for good – murdering justice-dodging criminals.

Dexter now knows that Harry wasn’t whiter than white. But poor Deb still idolises her cop dad and longs to be like him.

But though Deb’s coveted detective’s badge looks far from reach, Laguerta’s evil plan hasn’t completely worked. Laguerta wanted to divide and rule by making newly-promoted Sgt Angel Batista (David Zayas) stick the knife in Deb on his first day in charge.

The plan failed when the angelic Angel invited the mutinous Deb on a pub crawl with all the team and Laguerta watched in impotent rage as they left the office.

Watch your backs, people.

Gillian Crawley