Solution
1. Nd5! attacks the defender of the black queen and at the same time threatens Nxf6+ and Nc7+
1. Nd5 Qxf3 2. Nxf6+ Ke7 (attacking the knight) 3. Nd5+! (using a tempo-move to retreat the knight to safety first) Kd7 4. gxf3 wins a piece in the process.