Geordie is called to investigate an apparent break-in at a computer laboratory and suspects foul play when the lab head, Cambridge professor Simms, drops dead from mercury poisoning. It seems the deceased recently spent the night in the lab with someone other than his wife, possibly a fellow educated man. Geordie seeks advice from Leonard, who is now seen as Sydney's successor, and the pair start to uncover the surprisingly messy love lives of Simms' colleagues, but also a crucial frustrated ambition. Cathy is brutally tricked at work. Will returns to Grantchester and Mrs C, his staunch opponent, is shocked to discover his Greek persuasion, hence turns pro-Will when the archdeacon arrives to settle the succession, which Leonard accepts without any argument.
—KGF Vissers