It's the beginning of the end…of February AND of Broadchurch, although the latter is finishing for good, and unless things go really pear-shaped over the Atlantic, we'll probably see another February.

Broadchurch is back for the last time as writer Chris Chibnall performs a swan song before defecting to the BBC to take over as the new show-runner of Doctor Who, just as Peter Capaldi does a, ahem, show runner.

But back to the matter in hand: it's three years since the events of the previous series which, for those of you who can't instantly recall what it was about (or didn't watch it), focused on the fallout from the murder of Danny Latimer who was – keep up! – the young subject of the first series. Phew.

The series looked at how Joe Miller's trial affected his wife, former Detective Sergeant Ellie Miller (Olivia Colman), and Danny's family and also saw new revelations, namely the fact that Detective Inspector Alec Hardy (David Tennant) was protecting a witness in the failed Sandbrook child murder case.

Executive producer Jane Featherstone said: 'Chris' intention was always to inhabit a space which meant we could stay with our characters and our town after the crime has happened, to really examine the long-term effects of a tragic incident on a community. Our characters had lives before we joined them and they will continue to exist after we have gone.' Are you going to tell her, or am I, that Broadchurch isn't a documentary?

In addition to Colman and Tennant, Jodie Whittaker and Andy Buchan are all back again, bolstered by Julie Hesmondhalgh, Sarah Parish, Lenny Henry, Mark Bazeley, Georgina Campbell, Charlie Higson and Roy Hudd.

In the opening episode, Ellie and Hardy are called out to attend to Trish Winterman (Hesmondhalgh), who has reported a serious sexual assault. It's clear she has been raped, but cannot tell the police where the attack happened, or who carried it out.

A clue found at Trish's home eventually leads them to the crime scene, but it's a difficult setting and one that proves difficult for the forensics team to work in. But, perhaps more disturbing than anything else, is the fact that evidence suggests it was not an opportunistic act, but rather a cold, calculated and planned one.

• Broadchurch: ITV, 9pm