Christmas in Adelaide promises to be a pleasant vacation for Andrew Basnett, retired professor of botany and amateur sleuth. But the shadow of an unsolved murder hangs over the lives of his hosts, Tony and Jan Gardiner. The police still suspect Jan of her first husband's murder and it doesn't help when a second killing takes place under the same bizarre circumstances. What can a guest do in such a case but try to clear his hostess and solve the crime?