Solution
There is already an eye in the corner, but Black needs to create a second eye. is the only way to make it, setting up the ko at .
continued ( and elsewhere)
Black plays elsewhere as a ko threat. If replies there, captures back the ko.
Black lives potentially
White can't recapture the ko immediately, so Black has a chance to make life by a or b next.
Failure
After connects, destroys the eye. Now Black is dead.
Referenced byBeginnerExercise33