BQM 2 / Solution

Main line  

If White plays one of the points marked a, Black follows up at b to almost fill Black's eye space with a bulky five, killing White.

If White does nothing, Black can try to kill the corner as follows:

Killing demonstration  

Suppose White has fixed up her chain and Black filled the outside liberties, then Black can capture at 1 and the large white string is in atari. White can do nothing to prevent this.

Variation  

If White allows Black to connect to the outside, there are only false eyes at the marked spots in addition to the eye at 1-2.

Failure  

If Black plays 1 here, White grabs the vital point. Black 3 prevents her from making two eyes but creates a bent four shape. White can capture them to create a living shape. The only thing to check is whether there are not some peculiar things in the corner:

Continuation  

Black can make an eye but White puts his stones into atari.

Continuation  

So nothing bad happens to White. ( is not even necessary; dies in gote)