Anastasia's Mate is a variation on the simple Rook-Knight checkmating pattern and mating net with an open h file. "This checkmate got its name in a novel by W. Heinse, Anastasia and Chess (1803)."
[Quoted from: http://www.chesscity.com/ANALYSIS/Beginner/checkmate_patterns.htm]
The Knight controls two squares of the six-square rectangle anotomy of mate pattern preventing the opposing King's escape while the Rook delivers checkmate in the open h file, with the aid of an opposing piece and pawns blocking the opposing King's escape to other squares in the six-square rectangle anatomy of mate pattern.
Diagram of a Anastasia's Mate:
As with all of the Rook-Knight mating patterns, there must be assistance rendered by another piece or pawn to block the other possible escape squares in the six-square rectangle anatomy of mate pattern...in this case Black's pawns at f7 and g7, and Black's Rook at f8.
Other diagram showing Anastasia's Mate
The position above starts out with the same Knight move (Nd7+), forcing the King to h8 (Kh8). In this position, Black's pawn at h7 blocks Black's King move to h7 unlike the simple Anastasia's Mate. Now, White employs what is perhaps the single most important, deadly tactical move in a player's arsenal in an endgame...Queen sacrifice. Qxh7+!!, followed by Kxh7 "killing two birds with one stone" with a discovered checkmate via capture of Black's Knight and mate...Rxh5#; yielding the mating net in the simple Anastasia's Mate from a more complex position.
The game in action:
End of Part 1 of Anastasia's Mate.
(Next part is a Anastasia's Mate game)