When Peter discovers that, as the Duke of Denver, he is the Visitor - that is the ultimate regulator - of St Severin's College, and the fellows appeal to him to solve a dispute, he and Harriet, set off happily to spend some time in Oxford, scene of their engagement and wedding.

But the dispute turns out to be embittered.

It concerns a valuable manuscript that some of the fellows regard as nothing but an insurance liability which should be sold to finance a speculative purchase of land. The voting is evenly balanced between the party that would sell and the party that would keep it - evenly balanced, that is, until several of the fellows unexpectedly die.

And the causes of death of the deceased fellows bear an uncanny resemblance to the murder methods in Peter's past cases - methods that Harriet has used i her published novels.

The Warden has a casting vote - but the Warden has disappeared. And everyone involved seems rather more passionate about the decisions than reasons suggests they ought to be.