Professor Andrew Crompton, an amateur astronomer, is found dead in the university observatory after visiting a priest for confession. A note-book belonging to student Jez Haydock is found by the body and Jez's tutor, Gwen Raeburn, is quick to go through the dead man's belongings. The widow believed her husband was having an affair and obsequious porter Roger Temple names Ella Ransome, a G.P., as the other woman - and then she too is killed. Roger proves to be a manipulator though not a murderer but his father knows the identity of the killer. He's a retired porter, now in a home where he is regarded as senile and deluded but Lewis needs him to get to the truth.