Humphrey (Kris Marshall) has his hands full with a flurry of seasonal cases, while Martha (Sally Bretton) is busy with a task of her own.
Enlisting the help of Anne, Zoe and a special guest she races to pull off a secret plan.
With an influx of unexpected visitors, a slew of holiday crimes to crack and a heartwarming reunion on the line, the team struggle to juggle it all and still be ready for a life-changing reveal.
Adrian Edmondson and James Lance guest star. (S, AD, HD)
• Repeated on Wednesday at 2.00am on BBC2