Apple Tree Yard may have ended its self-contained story with all plot points addressed, but there could soon be source material for a second series. Writer Louise Doughty confirmed she's penning a sequel to her book that the hit BBC drama is based on. And it’s all going to be about Mark Costley.

Although the character suffering from a high-functioning personality disorder was found guilty of manslaughter at the end of the book and TV show, Doughty wants to continue his story.

“There’s a lot more exploration to be done,” she said to The Sun. “What happens to a fantasist when his fantasies are revealed to be dust? This is a man who has lived by this image of himself all his life, as a lothario and someone heroic.”

This means that the sequel would start with Costley (played by Ben Chaplin in the BBC series) released from jail. “I reckon Costley emerges from prison a broken man, so how does he put himself back together?” asked Doughty.

Would he attempt to get back with Yvonne, breaking apart her family life? How would his disorder impact his prison life? And could he kill again? All depressingly dark questions we’ll have to wait for the answers to.