A good Samaritan pensioner and former nurse had £5,000 of her savings stolen after going to the aid of a woman faking illness.
The 78-year-old was followed from a bank by two women, one of whom pretended to be unwell when she stopped at a butcher's, Scotland Yard said.
Her accomplice cut into the fabric of the pensioner's shopping trolley while she was distracted and swiped the cash, which the kind-hearted elderly woman had withdrawn to give to family members after the death of a relative.
Pc Susan Nash said: "This is a horrible crime that has left the victim stripped of her independence. She's now afraid to leave the house, scared she could be followed again.
"This is a victim who gave her life to caring for others as a nurse, who wanted to use some of her life savings to help her family.
"We urge anyone who has any information to get in touch."
Detectives released CCTV on Friday of a woman they believe was involved in the theft, which happened in Brixton, south London, on July 21.
The pensioner withdrew the money from Lloyds TSB in Brixton Road at around 1pm before walking to the nearby Market Row shopping arcade. While she stopped at Dombey Meats the two women carried out the theft.
The victim carried on shopping before later discovering the incision in the trolley and the money missing.
The suspect police want to question is described as an Asian woman in her 20s who was wearing a dark headscarf and dark clothing.