A man and a woman who tried to rob a man at knifepoint in York fled after one of them was bitten by their would-be victim's dog.
The man, aged in his early 60s, was confronted by the pair on Pateley Place on Saturday evening and threatened with a knife.
But the would-be victim's dog bit the man while the owner lashed the woman with the dog lead.
Police have appealed for witnesses to come forward.
The woman was about 30-years-old, white, approximately 5ft 3in tall with a thin build and blonde hair.
The man was in his mid-20s, white and approximately 5ft 9in tall.
At the time he was wearing a dark coloured sweatshirt and jeans.
Det Con Mo Mohammed said: "As the man screamed when he was bitten by the dog, I am sure that someone will have heard him and ask that they contact me as soon as possible.
"I would also like to hear from anyone who knows a man who has recently suffered a dog bite to his arm or may have treated the injuries for him."