A couple stole money and jewellery from an elderly woman.
People are treating the incident which took place at 4pm on Thursday in Thakeham Drive, Goring, Worthing, as a distraction burglary.
A Sussex Police statement said: “A man and a woman knocked on a woman's door, and acted like they knew her and asked to come in. The woman wasn't sure she recognised them but let them in.
“The man asked to use the toilet while the woman sat with the elderly woman in the living room.
“They then left and the victim felt suspicious about what happened. She checked her bedroom where she found £100 of cash and some jewellery had gone.”
DC Jamie Carruthers said: "The man is described as being white, in his 40s, between 5' 8" and 5' 11" and stocky. The woman is described also as white and her 40s with long straight brown hair tied back in a ponytail.
“These people have taken advantage of this woman by leading her to believe she knows them. If you are not sure who people are at your door, don't let them in and ring someone you trust. If you feel suspicious call the police on 101.”