A game starts 1 e4 and ends on move five when a knight takes a rook, delivering mate. What is the game? Every puzzle collection should have one really tough problem, and here it is! I remember GM Mestel showing this puzzle in the hotel lobby during the 1976 Haifa Olympiad. Soon there was a group of more than a dozen leading players clustered silently around a chessboard on which the move 1 e4 had been played. One of hotel staff came up to see what had attracted such a crowd, but when he saw what they were doing, he went away shaking his head in disbelief at these crazy chess players.

Anybody who solves this puzzle in less than 24 hours (without looking at the hint-coming up next) is doing very well indeed.

Hint- First of all, we have to decide who delivers the mate. If White mates, then there is half a move less to play with, and in addition White is committed to 1 e4. It turns out that the four remaining moves are insufficient to arrange a mate, so it is Black who plays the mating move. The (fairly large) hint is that Black cannot deliver the mate using only the knight. It is necessary for another piece to be brought into the game.

There is not really any logical way of deducing the solution, which of course is why it is so hard. You just have to try various ideas until one of them works. Perhaps the key idea is that the problem is impossible so long as Black relies only on the knight. Another piece has to enter the game. The solution runs...