Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bc4/3...Nf6/4. Ng5/4...Bc5/5. Nxf7/5...Bxf2/6. Kf1/6...Qe7/7. Nxh8/7...d5/8. exd5/8...Nd4/9. d6

9. d6
Taking with 9...cxd6 blocks Black's queen in and White can safely play 10. Kxf2. Thus 9...Qxd6 is the stronger move.