Steve Punt returns as Radio 4's very own private detective.

Punt travels to Paris to investigate the suspicious death of celebrated writer Émile Zola. Zola died in 1902 from carbon monoxide poisoning caused by a blocked chimney. At the time, the authorities reached a verdict of accidental death. Subsequently, evidence has emerged that Zola's death may have been murder.

Certainly Zola's role in France's notorious Dreyfus Affair made him many enemies. But as Punt discovers, the case is far from clear cut. For one thing, carbon monoxide is a very unusual way of murdering someone. Punt summons the experts and weighs up the evidence.

Producer: Laurence Grissell.