A man was hit with a baton and robbed of his mobile phone and some cash after a gang of four broke into his home in Montagu Street, Kettering.
The 45-year-old victim heard voices outside seconds before four men forced entry to his flat and hit him with a baton, causing an injury to his arm.
The incident happened just before 9pm on Wednesday, October 28.
The offenders were all white and wore dark clothing with their faces covered.
They had local accents.
Witnesses, or anyone who knows anything about the incident, can call Northamptonshire Police on 101 or Crimestoppers anonymously on 0800 555111.