A man who knocked on the door of his victims' house pretending to be a gas engineer allegedly stole two phones, a charging point and a purse from the property.
The incident occurred at 10pm on Monday (May 16), in the village of Haddenham, near Ely.
The individual knocked on the door of the property, and said he wanted to check the boiler.
When the victims - who were described as vulnerable by Cambridgeshire Police - refused him entry, the man allegedly stuck his foot in the door and forced his way in.
The man, described as large, reportedly took the items and made his escape in a green Volvo.
Police constable Andy Smith, of Cambridgeshire Police, said: "This was a terrifying incident for the vulnerable victims.
"I would like to appeal to anyone who may have seen a green Volvo in Haddenham at about 10pm on Monday (May 16) to get in touch with police immediately."
Anyone with information is asked to contact police online (https://www.cambs.police.uk/), or by calling non-emergency number 101, quoting reference 35/34408/22.
Information can be given anonymously by contacting the CrimeStoppers charity on 0800 555 111.
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