In the novel Sleeping Murder, Dr McGuire was the superintendent of Saltmarsh House, a sanatorium in Norfolk, at the time that Kelvin Halliday had been a patient there. He was no longer there some twenty years later when Gwenda Reed visited the place to inquire about Halliday who was her father. McGuire had however kept Halliday's diary among his case notes and Dr Penrose handed this to Gwenda.
BBC's Miss Marple
McGuire is mentioned in the same context in the BBC 1987 adaptation of the novel. Dr Penrose who met Gwenda and Giles told them that he was McGuire's junior. He briefed them on Halliday's case from Dr McGuire's extensive case notes and also handed over Halliday's diary.