Guards Guards - Cobbles

As Vimes half-rose in horror Errol escaped from his grip and cleared the trough in one leap. He bounced across the plaza in a series of wing-whirring arcs, mouth gaping, emitting wheezing burps, trying to flame.

He was answered with a tongue of blue-white fire that melted a streak of bubbling rock several yards long but failed to strike the challenger. It was hard to pick him out of the air because, quite clearly, even Errol didn't know where he was going to be, or what way up he was going to be when he got there. His only hope at this point lay in movement, and he vaulted and spun between the increasingly furious bursts of fire like a scared but determined random particle.

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Guards Guards - p201