[1] It was the twelfth in a series of novels featuring Inspector French and takes the form of an inverted detective story, the second Crofts wrote that year after The 12.30 from Croydon.

A cement-producing company based near Hamble discover that a rival across the Solent near Cowes on the Isle of Wight has begun producing cement with a new formula that is undercutting them and threatening their financial recovery from the Great Depression.

Things begin to go wrong for them when Chief Inspector French is assigned to the case, swiftly proving it couldn't have been an accident.

On top of this the company are approached by the directors of their rival who, having unearthed evidence tying them to the killing, essentially blackmail them into agreeing to a business deal on very generous terms.

When shortly afterwards the launch carrying the blackmailers back across Southampton Water explodes, drowning two of them, French follows up the case with renewed energy.