Cash, jewellery, a handbag and a Playstation were all taken from a home in Hemel Hempstead on Friday, May 26.
The break-in occurred between 9.15am and midday when offenders broke into the house on Craigavon Road, Grove Hill, via a rear window.
This followed a suspicious incident at the address one week earlier, when a teenage male knocked on the door claiming that a ball had gone into the garden of the property. When the garden was checked no ball was found.
Detective Constable Chris Phillips said: “The teenager who knocked at the door was aged approximately 17-19 years old, had medium-length dirty blond hair, and was wearing a grey jacket.
“I am appealing to any who has any information about this incident to come forward, in particular if you saw a man of this description in the area at the time or in the days or weeks before the break-in occurred.”
Anyone with information should contact Herts Police on101, quoting crime reference number D1/17/4266.
Alternatively call Crimestoppers, anonymously, on 0800 555 111 or online at www.crimestoppers-uk.org