With no other option, they say the man held on to the woman with one arm and called the police with his cellphone.
Then, as the man again attempted to get away, police say the woman encouraged a nearby group of men to attack him.
The man, who is black, was stabbed in the chest, struck with a piece of wood, kicked and punched by a group of as many as six white men, who fled after the attack.
The victim was taken by taxi to the Grey Bruce Hospital Centre, where he was listed in serious but stable condition after undergoing emergency surgery.
The man had been in Owen Sound working for a hydro company, and it appears his attackers did not known him, said Owen Sound police Sgt. Ted Kitto.
One suspect was arrested and more arrests are likely, Kitto said.
He added that police havenÂ’t determined whether the attack was racially motivated, but said the incident is still under investigation.
Shawn Dyer, 19, has been charged with assault with a weapon and aggravated assault.