Clusters, one of the great country houses, is troubled by bats. Sir John Appleby cannot help, but when Lord Osprey is found stabbed with an oriental dagger in the library the ex- Commissioner feels this to be more of a challenge he can take on. The house guests include another title, a QC and some experts on numismatics who are particularly keen to find out where the late Lord concealed his collection of antique coins. The bats have the last word.