A 77-year-old man had his hands injured and his mainland girlfriend, 43, suffered cuts to her chest, left hand and legs in a fight at a public housing unit in Sau Mau Ping yesterday. The couple started fighting during an argument in their Tin Hang House flat at Shun Tin Estate around 9am. Officers seized a bloodstained knife in the unit. The man was in stable condition and the woman was to undergo surgery last night. Police said the pair had been arrested and investigations were continuing.