FREE - In Google Play
FREE - in Win Phone Store
I believe there is a mistake in a lesson called "deadly diagonal", code ECP068, from the course "essential checkmate patterns by FM Thomas Wolski.
Not sure how to get the link, but it may be:
On the first move, if you play Qc6, it is described as an incorrect move, since "This slow queen move allows White to do whatever he wants. He could, for example, capture your b7-bishop."
As far as I understand, if white captures as suggested (2. Nxb7 is the only way to do that), then 2... Qxg2 is mate.
I don't think Qc6 is the best move - since there are ways to defend against it (2. Nce4, 2. Nge4 and maybe others), and there is another mate in 2, which is the main line of the problem. However, this does make the explanation provided irrelevant.
I may be wrong, in which case I would appreciate it if someone would point it out to me. Otherwise, I hope this can be corrected. I'm hoping that reporting it here would be enough to bring it to the attention of whoever should be aware of it. If there's another way to report it, please let me know.