A delightful mate in 4 to end the week. There are lots of mates in 5, but only one mate in 4!
I love the key move of this solution. Talk about mysterious rook moves! 1.Re1 f5 [1...Kh5 2.Kxf6 Kh6 3.Rh1#; 1...e5 2.Rf1 f5 3.Rxf5#] 2.e5 f4 [2...Kh5 3.Kf6 Kh6 4.Rh1#] 3.exf4+ Kf5 [3...Kh5 4.Rh1#] 4.e4#