Double check
A double check is the most forcing move in chess. You make a double check by using a discovered check and also checking with the piece that you move. The only way out of a double check is to move the king, so often a double check is checkmate!
Black decides to attack White's Queen with ra4 assuming that White must move the Queen but there's a double check available.
Any move from the knight delivers a check with both pieces and the King is forced to move and the Queen is safe.
And the Queen gets out of danger and delivers checkmate protected by the recently posted knight on e7.