Wife set up camera in clock after becoming suspicious when her husband gave her a glass of water containing hydrochloric acid

It is, in the words of the prosecutor, a story that "could have come straight from the pen of a whodunnit writer".

A retired Italian carpenter has been arrested after his sleuthing wife suspected he was trying to poison her and set about trying to prove it with the help of a spy alarm clock bought on the internet.

The drama began in February in the northern Italian town of Dalmine, where the couple had reportedly lived for almost 40 years. The 61-year-old woman grew suspicious when some water brought to her by her husband created a burning sensation in her mouth.

The woman, who has not been named, sent it off for tests in a laboratory, which, when they came back, revealed the presence of hydrochloric acid.

Perturbed, the woman became even more worried when she found a bottle among her husband's things that had no label on it and was filled with a clear liquid. She sent that off to be analysed, as well, and was told that it, too, was hydrochloric acid.

Police confirmed that she then took advice from relatives and bought a miniature video-camera-cum-alarm-clock, proceeding to film her husband in the kitchen.

When, at the end of March, she felt she had enough evidence, she went to the police. Her husband was arrested on Easter Saturday and is being held in detention on suspicion of attempted murder.

The man admits putting poison in his wife's water but denies trying to kill her. He told police he had been trying to make her a little unwell to ease her obsessional interest in planning pilgrimages and listening to the Catholic radio station Radio Maria.

The man's lawyer declined to comment when contacted by the Guardian.