A little life and death to go with your morning tea

I was working on Problem 24 in the excellent Just Go software:

And I thought the program was broken because I thought C3 was a good move for Black. But once I loaded the position into Katrain, I saw that C3 did not work and that another move would save Black…. but I’m not going to tell you 🙂

Here is the sgF file for your perusal.