Plaskett's Puzzle is a chess endgame study created by the Dutch endgame composer Gijs van Breukelen (February 27, 1946 – December 21, 2022) around 1970, although not published at the time.
Van Breukelen published the puzzle in 1990 in the Netherlands chess magazine Schakend Nederland.
According to contemporary accounts, of the several strong grandmasters who analyzed the position, only former World Champion Mikhail Tal was able to solve it.
[1] While the solution is striking, the study was found to be flawed in that White has no immediately decisive continuation if Black plays 4...Kg4 rather than the obvious 4...Nf7+.
[2] This issue may be fixed by instead placing Black's g5 knight on h8 or e5, or by adding a white pawn on h2,[2] but the flawed version of the study demonstrated by Plaskett and published by van Breukelen remains the best known.