A man was injured as he tried to prevent a burglary in Burton Latimer.
The man disturbed three youths who had forced entry to the rear of a property in Churchill Way at about 5.45pm on Thursday, April 11.
One of the three threatened the man with a screwdriver, inflicting a scratch to his arm as the trio made their escape.
The offenders are described as three white teenagers, all aged between 16 and 19.
The first was about 5ft 8in, of average build with blond hair. He was wearing a black baseball cap and a black scarf across his nose and mouth.
The second was also about 5ft 8in, smaller than his accomplice, and wearing dark clothing including a baseball cap and scarf.
The third was 5ft 8in, slim and wearing a black tracksuit with a scarf and baseball cap.
Witnesses or anyone with information are asked to call Northamptonshire Police on 101, or Crimestoppers in confidence on 0800 555111.