Team 45 45 league action

Today I played my round 5 game in the team 45 45 league on Internet Chess Club (ICC). See affiliate links on this website!) My team was in the lead 2-1 so I just needed a draw but I had the Black pieces.
On move 12, the server had an outage and when I reconnected, we couldn't get the game back. So, we played a new one and followed the same opening until..... My opponent deviated on the last move, instead of following the book with Nxd4 sacrificing a pawn, he chose Nd6+ which got me out of the book. From here I had to do the work myself and I actually managed to play a good move in the position below.

What would you play here and how far can you see?

​BLACK TO MOVE

 
1. ... Be4!! (My engine gave me the !!) threatening mate on d1. 2. h4 Rd1+ 3.Kh2 Bxf3 4.Kg3 Bc6 and White gets mated after Rxg2+ and Rh1.