DI Purbright and DS Love investigate the disappearance of a Mr. Hopjoy after receiving an anonymous letter saying the man had disappeared. The search of his house reveals a number of suspicious elements including blood and a carboy that once contained acid. As they look into his background, they learn that he was frequently absent for days at a time and was, to put it mildly, a libidinous fellow. He lodged with Gordon Periam, a tobacconist who, the pipe smoking Purbright notes, doesn't smoke. Periam is missing however, as is Hopjoy's car. While the results of the forensic examination of the house is still outstanding, Purbright learns from his Chief Constable that Hopjoy was something of a spy and that two of his colleagues, Tozer and Barraclough will be conducting their own investigation.
Purbright and Love locate Hopjoy's car which has been borrowed by his house mate Gordon Periam who, it seems, is on his honeymoon having married his fiancée after the recent death of his mother. Periam thinks nothing of Hopjoy's absence as thee were frequent and sometimes lengthy. They soon start to pull together the information they need to solve the case. The forensic analysis reveals that blood found in the bathroom was from a pig as were the acidified remains found in the drains. In fact, a pig had been stolen from a nearby farm as was a carboy of acid from a garage. Hopjoy was heavily in debt as well owing respectable sums to all types of merchants in the village. It all leads Purbright to an inevitable conclusion. The police are soon onto a new case when when a middle-aged woman, Mrs. Banister, apparently disappeared. The case has similarities with the disappearance of another 2 months previously.
DI Purbright and DS Love are convinced that they may be dealing with a man who is preying on middle-aged women and decide to focus on matrimonial agencies to see what might turn up. Sure enough, they soon discover that both of the missing women had registered with the same agency and were possibly exchanging correspondence with someone. They visit the local agency acquiring the name of a recently joined member, Miss Teatime but she rebuffs them insisting that she can take care of herself. When she's contacted by Mr. Trelawny, it soon becomes apparent that she is quite capable of doing so and she's even prepared for Mr. Trelawny's accomplice.
Several otherwise reputable sexagenarian Flaxborough men seem to be under the influence of a potent aphrodisiac in a series of assaults on local women.
Purbright traces the drug affecting the male senior citizens in Flaxborough to either a herb supplement or an experimental prescription drug.
After the death of Harold Carobleat, his wife is shocked to find that he has left his estate to a neighbor who is subsequently found electrocuted.
When a third member of the quintet of prominent Flaxborough citizens is murdered, Purbright uncovers the covert prostitution ring behind them.