involves some sacrifice tactics.
White sacrifices , and then makes two eyes by capturing and , leaving the marked stones unprotected (Black can play at a later on, to capture them in a snapback). Note that White's liberty at b is crucial; if not for it, at c prevents . See J-group#straight J-group.
At several stages, White can make a mistake.
This is the sort of bad move that could be in the (imaginary) book Get Strong At Gote.
Simply connecting is not good enough. After , Black will be able to almost fill White's eyespace with a killing shape.