Dean jumped back as the ground in front of them started to give. He grabbed Seamus's mum and shoved her back, knocking her clear but stumbling himself as the alleyway ground cracked and opened. Multiple thoughts raced through Dean's head but most prominent was the fact that this woman, whoever she was, had killed Penny and pretty much bested an Auror. If she was behind all these murders, maybe she'd even killed Harry.
Rage filled Dean, rage tipped with fear. If Harry and Ron had both been unable to kill this witch, could he manage to get himself and Mrs. Finnigan away safely? Mrs. Finnigan, her eyes still blazing, cast another incarcerous, higher this time, intending to bind the woman's arms as Dean got to his feet. His first severing charm missed. Maybe the second would, so he cast it again.
Two against one. Those odds had to be in their favor, right?