makes the living eyeshape of bent four. a and b are now miai to keep this eyeshape and prevent it from being reduced to straight three. Black lives with 4 points.
here doesn't work. After
, If White plays a, Black plays b; and vice-versa (that is miai).
The most tempting failure is probably the atari at . White ignores it and reduces Black's eyespace by
.
Black's capture is answered by the nobi of and if Black finally protects his eyespace, it is already reduced to straight three and White plays the killing move
.