A spate of thefts from gardens and washing lines in a southern English town had been baffling the Bobbies.
Socks, gloves, ladies underwear - almost anything left unattended was fair game for the thief, especially the knickers, and the rate of offending was getting worse.
But now the culprit has been unmasked as a kleptomaniac cat with a generous nature.
Eager to please his new owners, Peter and Birgitt Weismantel, 13-year-old Oscar had been bringing home presents to the family home in Portswood, a suburb of the southern coastal town of Southampton.
"He started bringing socks home a few months ago and then gardening gloves which we tracked to our neighbor," his owner Peter Weismantel told the Southern Daily Echo newspaper.
"Then we had a situation in which he brought back young women's underwear," said Peter, 72.
"It began to escalate and I telephoned the police as people must have been missing clothes - especially with women's underwear being taken."
The couple have been fostering Oscar from Southampton's Cats Protection charity since last Christmas.
Since then he had also pinched builder's gloves, a knee-pad, a paint roller, rubber gloves, and 10 pairs of children's underpants.
On average he commits 10 robberies a day.
"He brings them back as presents," Birgitt told the Echo. "We can't give him back now as he makes such an effort with all these gifts. He's got a lovely personality and is a very loving cat.
"I think we fell in love with him before he started taking all these things," she added. "It was just so touching to see him come home every day with something for us."
Now the couple will adopt Oscar full-time but they still have yet to devise a way to curb his criminal instincts.
"He's still doing it now," said Peter. "We are thinking of training him as Fagin!"