Sent out by his London newspaper to write an article on Matthias, the famous visiting violinist, Peter, his friends and family become involved in some complicated foreign intrigue. Peter's curiosity is aroused when Mr. Matthias feigns illness on the trip from the airport and is bedded down in Peter's household. The subsequent fervent search by Elkin, a ""friend"" of the musician's, for a piece of music actually sparks more intensive investigations. Clue after clue leads to uncovering a spy ring transmitting vital atomic information through a code of musical notation, unwittingly carried from country to country by Matthias. Despite the attempt at suspense, the mystery falls on several counts, particularly its overabundance of cluttered detail and its reliance of final explanations to tie up the loose ends.