The fascination of an Agatha Christie whodunnit is the plot.

It’s an intellectual maze with twists and turns and dead ends, literally. Most of the characters are two-dimensional, at best.

Verdict, which opens the post-panto season at Bath, is a little more complex. While it doesn’t rely on characterisation, personality or emotion for its framework, all three elements are much more in evidence than in most of Agatha Christie’s work and therefore it is a more meaty drama.

It’s not strictly a whodunnit. We know who the culprit is, but an innocent party is accused. The victim (Cassie Raine) is the sick wife of an immigrant professor, who was forced to resign from his job at a university in an unspecified European country for supporting a colleague who fell foul of the political regime.

He’s a good man, kind, compassionate and highly principled and the drama shows how such a paragon can be very hard to live with, and unintentionally harsh on those nearest and dearest who have to suffer the consequences of his moral rectitude.

Robert Duncan, more familiar in comedy roles such as Gus in Drop the Dead Donkey, is totally credible as the professor. His thoughtful performance was the linchpin of the play.

Dawn Steele was equally multi-faceted as his wife’s cousin Lisa, who lived with them and took care of Anya (Cassie Raine) his wife.

One-time pop-star Mark Wynter proves he made a smart move into straight theatre with a strong performance as the doctor.

Elizabeth Power has a ball as the busybody, melancholic charlady in complete contrast to Ali Bastian as the archetypical ruthless little rich girl, Helen Rollander.

Some of the characters are wooden Christie stereotypes, not the actors’ fault. But there are enough believable personalities to make this one of her best puzzles which keeps the suspense buzzing to the last.

It runs until Saturday.