Doctors, Caroline Quentin makes a guest appearance as Howard Bellamy's sister.

Quentin is playing special constable Saskia Cook, who arrives at the local police station to be paired with Howard.

Rob Hollins 'introduces' the pair but soon notices that there is already a history between them, which he tries his best to stay out of.

Caroline Quentin as Saskia Cook

Being reunited with Howard gives Saskia a chance to question why he makes so little effort with their mother, reminding him that she will be 80 this year.

Howard avoids the issue, but he may have underestimated his sister's powers of persuasion when she later ropes him into karaoke after a busy day on the beat!

Saskia and Howard do karaoke

Airs Wednesday, June 10th