Some Days .....

are just not meant for playing chess.

I just finished this blitz game when my opponent ran out of time. A couple of moves before the end, we arrived at this position.

White had just played

1. Rc1

Now what is the quickest path to victory for Black?

I totally didn't see it and played another move instead (D'oh!)

What was it that I missed?

Answers can be found by highlighting between the brackets.

[The killer move was:
1..... Qc3!!
White has no defence as the Queen must be taken else it's mate in 1.
2. Qxc3 bxc3
and now White cannot stop mate in 2 by Black after
3.... Rb8+ and 4.... Ra1#]