September means many things: that back-to-school feeling, even though you left school 15 years ago. Lamenting the lack of BBQs you went to this summer (One! I went to one). And most excitingly, the return of thriller season.

And we’re kicking things off with a bang with series three of The Tower, the powerhouse thriller set in London that’s fearless in tackling the big topics that permeate society and policing.

Gemma Whelan stars as DS Sarah Collins who, in season one, led the investigation into the death of a policeman and a young teenage girl who had fallen from a tower block – and the subsequent disappearance of police officer Lizzie Adama (Tahirah Sharif), who was having an affair with a married superior, DI Kieran Shaw (Emmett J Scanlan). Season two saw Collins investigating a cold case – the death of a young teenage girl – while a domestic violence case was also underway.

Series three of the show, adapted from former Met police officer Kate London’s crime novels, will follow as she tries to solve the stabbing of a teenager alongside the undercover investigation into a criminal gang led by DC Steve Bradshaw (Jimmy Akingbola).

We talked to Whelan, whose TV career includes Game Of Thrones, Gentleman Jack and Funny Girl, about everything you can expect in series three of the satisfying thriller, which launches at 9pm on Monday 2 September on ITV, as well as her fascination with missing cat posters…

The Tower season 3: “It’s TV you’ve got to put your phone down for”