Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bc4/3...Nf6/4. Ng5/4...Nxe4

= Two Knights Defence =

4...Nxe4?
Not the best move for Black. Ignoring the threat of White's position, they grab the e-pawn. This initially seems like a good move because Black has 5...d5 after 5. Nxe4? forking the knight and bishop.

However, White can now capture Black's unprotected f-pawn with check: 5. Bxf7+ Ke7 6. d4! and Black cannot yet take on g5 without losing his queen.

5. Nxf7 is a mistake, as after 5... Qh4 Black gains an advantage even against White's best defense.

Theory table
1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6 4.Ng5 Nxe4