The soap favourite, played by Pam St Clement, 65, will be run over after discovering disturbed Steven Beale is behind the disappearance of half-sister Lucy (Melissa Suffield, 15).
As the veteran star, dubbed Fat Pat by fans, races across Albert Square to tell his dad Ian (Adam Woodyatt, 39), she is struck by Roxy Mitchell's new 4x4.
Passengers Peggy (Barbara Windsor) and Ben (Charlie Jones) jump out of the vehicle to find Pat lying motionless on the ground.
After being rushed to hospital, grandson Steven, played by Aaron Sidwell, 19, visits her in A&E to prevent her from spilling the beans.
He will be seen trying to smother her while she lies in bed.
The dramatic scenes will air on Monday on BBC1.
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