We were halfway up the third when I heard the metal fire door crash open, accompanied by the ripping discharge of a machine pistol. The bikers had figured we might be trying an ambush, and weren't taking any chances. I wished for a grenade or something equally unpleasant to send down the stairs to keep the kids occupied, but of course I never carry the gift that's appropriate to the occasion. Another half-flight, and I heard the sound I'd been dreading: the whine of a high-revving turbine. Friend elf had brought his bike and was assaulting the stairs. We didn't have long.