The incident took place at around 7.15pm last night (Wednesday) when the offender entered the property in Northampton Road.
He was handed some cash for the bogus charity and then asked for a drink of water.
As the victim went to get it, a woman entered the house claiming that the victim’s taxi had arrived.
When the victim replied that she had not ordered a taxi, the woman left, followed by the man.
They ran up the road to a car that was parked on Westhill Drive.
The victim later noticed that further cash from her purse and bank cards were missing.
A police spokesman said: “The first offender is described as white, in his early 20s, of a thin build and around 5ft 3ins tall.
“He had brown hair which was pulled back and worn in a topknot.
“The second suspect is described as white, in her 20s and around 5ft 5ins tall.
“She was smartly dressed and with a short, blonde, bob hairstyle.”
Anyone with information can contact Northamptonshire police on 101.
Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555111.