The pause in the fight gave Sirius some time to react. It wasn't a lot but it was just enough to jerk back. Instead of landing in his throat, the dagger cut into Sirius's raised hand. He screamed as it went through the bone and jerked back. Blood poured from the wound and, if he survived this, he was going to have some real problems living through first blood loss and then possible infection.

What he needed to do was think. He was defenseless. He'd just been stabbed.

He was going to die in the next few minutes, if that.

Sirius tried to grab at his enemy's hand to wrest the dagger from him or at least delay getting stabbed again.