Henry Wilt is a demoralised and professionally under-rated assistant lecturer at a community college in Mid Anglia who is dominated by his psychologically immature wife Eva and thus fantasises about murdering her. During a night walk to relieve his frustrations, he accidentally busts an undercover operation by Scotland Yard Inspector Flint, earning him the latter's undivided attention. Three weeks afterwards, something that looks like a body is found in a construction foundation on the college grounds. Since its appearance coincides with Eva Wilt's mysterious disappearance the night before, and with the Wilts' abandoned car found nearby, Henry is quickly suspected and investigated for murder by Flint. Pleading innocence, Henry relates that the night before, he and Eva had attended a party hosted by their wealthy friends Hugh and Sally. Sally, who has grown tired of Hugh and has turned lesbian, wished to win Eva over to her side; when Henry caught her attempting to seduce his unsuspecting wife and confronted her in private, he ended up accidentally knocking himself out. Exploiting this opportunity, Sally stripped Henry down and tied an inflatable sex doll to him. When Eva saw him trying to wrest himself free, she was scandalised and fled to Eva, who subsequently invited her to a yacht trip on the local river. After being liberated, the humiliated Henry dumped the doll into the still-wet foundation at the construction site. Even though the evidence and the witness testimonies are ambiguous at best, Flint becomes obsessively fixated on the idea that Henry is a dangerous mass murderer currently wanted by the police. That attitude is exasperated even when the doll is recovered from the construction site, since Flint believes it to be a decoy set up by Henry and Eva's body was disposed of elsewhere. Due to lack of solid evidence, Henry is eventually cleared, but Flint continues shadowing him. In the meantime, Eva learns from Hugh about Sally's designs on her and her set-up of Henry. Fleeing the boat, she calls Henry from a church and apologises to him, asking him to pick her up. Unbeknown to her, the church's priest is actually the wanted mass murderer; as he prepares to kill Eva, Henry tries to come to her aid, only to be hindered by Flint. After they fight off the mad priest, Flint holds Henry and Eva at gunpoint, but his wild murder accusations are quickly deflated by Henry's alleged victims turning up alive at the scene, and the priest is arrested by an undercover officer. Reconciled with his wife, Henry joins Eva's tai chi class for neurosis therapy, where he finds Flint, on a leave of absence, as a new member to sort out his own psychological issues.
