A woman has been found dead with stab wounds, an hour after the bodies of her husband and two sons were discovered at the foot of cliffs in East Sussex.
Police found the woman, in her 40s, at the family home in Twickenham, south-west London, shortly before 18:00 GMT on Monday.
Her death is being treated as murder.
Sussex Police were called after three bodies - thought to be the woman's sons, aged seven and 10, and husband, 57 - were found at Birling Gap beach.
Scotland Yard said they were not looking for anyone else in connection with the deaths.
Detectives were called to South Road in Twickenham after concerns were raised for the welfare of the occupants.
Post-mortem examinations will take place in due course, they said.
Sussex Police said it recovered a vehicle near to where the three bodies were found at about 17:00 on Monday.
The house in Twickenham has been sealed off as forensic officers carry out their investigations.
One neighbour, Alicia Mede, said she believed the family were new to the area but had seen little of them.
"I saw Christmas lights on around Christmas time, but that was it," she said.