Final position — White is winning
The Knight opens the door for his brother
White wins in 12 moves with a decisive material gain. (50 Opening Traps,Part 1 - The Knight opens the door for his brother - B46 - https://lichess.org/@/CHESSLUCAFD)
The moves
| 1. | e4 | c5 |
| 2. | Nf3 | Nc6 |
| 3. | d4 | cxd4 |
| 4. | Nxd4 | e6 |
| 5. | Nc3 | a6 |
| 6. | a3 | Qc7 |
| 7. | Be2 | d6 |
| 8. | O-O | Nge7 |
| 9. | Ndb5 | axb5 |
| 10. | Nxb5 | Qd8 |
| 11. | Nxd6+ | Kd7 |
| 12. | Nxf7+ |
How the The Knight opens the door for his brother works
The The Knight opens the door for his brother is a classic chess opening trap arising from the Sicilian Defence. In this line White wins decisive material by move 12, punishing a natural-looking but losing idea from Black.
The full sequence runs 1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 e6 5.Nc3 a6 6.a3 Qc7 7.Be2 d6 8.O-O Nge7 9.Ndb5 axb5 10.Nxb5 Qd8 11.Nxd6+ Kd7 12.Nxf7+. Each move looks reasonable, which is exactly why the trap is so effective over the board — Black walks into it while trying to play "normal" developing moves.
This pattern is well known from master and correspondence play (50 Opening Traps,Part 1 - The Knight opens the door for his brother - B46 - https://lichess.org/@/CHESSLUCAFD). Recognising it early lets you either spring it as White or sidestep it as Black.
Practice this trap move-by-move
Open the The Knight opens the door for his brother in the Trapsterapp to play it out on a live board, drill it in practice mode, and learn how to avoid it when it's set for you — along with the full library of chess traps and gambits, fully offline.