A 71-year-old woman and her six-year-old grandson have been found dead in a pond at Holywell village, near Castle Bytham, Lincolnshire Police said.
The alarm was raised on Thursday night after the 71-year-old's daughter contacted police after being unable to contact her mother or six-year-old son.
The little boy had spent the previous night at his grandmother's home in Castle Bytham and had been due to return home to his mother yesterday evening.
Ground searches were conducted and an RAF search and rescue helicopter was called in to assist.
The elderly woman's car was found close to a duck pond at Holywell village at around 11.45pm last night. Her body was recovered from the pond but despite efforts to resuscitate her, she was certified dead at the scene.
The body of the child was not found until 4am today.
The circumstances surrounding the deaths are being investigated and post-mortems will be carried out in due course.