Officers were called to a residential address at Swinfield Close at 19:12hrs on Monday, 4 June to reports of concerns for the welfare of the occupants.
London Ambulance Service and London’s Air Ambulance attended.
At the scene a woman, aged in her 30s, and a one-year-old boy were found suffering stab injuries.
Both victims were taken to a west London hospital for treatment.
The boy remains in a critical condition.
The woman’s injures are not life threatening.
Enquiries are underway to trace a man who was known to reside at the address.
Work continues to establish to circumstances of the incident but at this early stage it is believed the parties involved were known to each other.
A crime scene has been established and officers remain at the scene.
Officers from Hounslow CID investigate.
There have been no arrests; enquiries continue.
Anyone with information is asked to contact Hounslow Police on 101 or tweet @MetCC quoting CAD 6981/4June. Alternatively, call Crimestoppers on 0800 555 111.