Masterpiece Mystery!

Inspector Lewis: Series III: Dark Matter (3x13)

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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.