1. d4 d5
2. e4 dxe4
3. Nc3 Nf6
4. f3 exf3
5. Qxf3?! (see diagram right)
The aim is to develop quickly, although the White Queen is depriving the g1 Knight of its most natural square. The d-pawn is en prise, and this is where the gambit can prove lethal should Black accept the pawn.
The game may continue:
6. Be3 Qb4?
7. O-O-O! Bg4? (see diagram right)
Now White plays 8. Nb5!!, threatening mate in one. Not only that, but the move shields b7 from its defender. It was Emil Josef Diemer who first played this move in 1934.
How can Black respond? The only move that prevents an early loss is 8... Na6, although correct play by White should give an advantage. Everything else loses quickly. For example 8... e6 (or ...e5) fails to 9. Nxc7+ Ke7 10. Qxb7! Qxb7 11. Bc5#. Or 8... Nbd7 9. Qxb7 Rb8? 10. Qxb8! Nxb8 11. Nxc7#.
Going back to the position after 6. Be3, Black is best advised to play ... Qg4, when White usually responds with 7. Qf2. The game remains double-edged, with Black's Queen exposed to various attacks.
Try it sometime (probably not in a league match!) and see how it goes.