Footsteps thud behind us. We throw ourselves against the wall. Callen squeezes his sphere with both hands and it becomes a marble, which he hides to conceal the glow. Yellow light spills onto the floor and an Official jogs out. Callen springs forward and whips the marble at him. The ball hits the Official’s back and his suit flashes white.

“What the—”

He turns around as the marble bounces off the floor and zooms back at us. I catch the orb, then hurl it at the Official again. He snags it out of the air, expands it into a sphere, and slams it against the wall. The sphere ricochets toward me and Callen, buzzing with an electric fizzle each time it hits the wall. We dive to the ground and the sphere zips over our heads, zooming out of the aisle.

The Official runs away and I look at the number above the shelter: 96.

Callen waves me forward. “Get moving.”

We jog down the corridor and turn left. Shouts echo around us and in our headsets. Tiny dots flare on the map display with each shout. Spheres and marbles whizz over the walls and bounce off the ceiling. We pass a ramp, turn, and jog toward a shelter.

A yell. The shelter flashes red.

A Recruit on the red team dives from the entrance, but the shelter purged already him. The sphere he’s holding drops through his hand and drifts toward me.

“Tough luck,” Callen says, slapping the Recruit on the shoulder as we pass him.

He grumbles and stalks away to an exit. I pick up his sphere. Callen glances backward, then ducks and shoves me down. A rogue sphere fizzles off the wall and zooms up the ramp to Level 2.

Still out of breath, Callen taps the side of his head and says, “Constant vigilance.”

We stick to a line of barriers and keep moving so as not to activate the purging sequences. I hear a grunt and spin around, then block my chest with the sphere I’m holding. A second one crashes into mine and ricochets over a barrier. I slam my sphere against the wall so it zigzags toward the person who snuck up on us—a girl on the blue team—but she ducks sideways and retreats.

“Didn’t have to throw that,” Callen says.

The rush leaves me shaking.

“Wasn’t thinking.”

We jog to the next intersection and I poke my head around the corner—then quickly pull back.

“Two. Red team. Both armed.”

Callen points to a shelter and we run to it. I prepare to jump out the opposite window slot, but the red players pass without checking inside.

“…six people by herself already,” one of them is saying. He’s talking about Glacia. He has to be.

When the voices fade, Callen looks outside the shelter again. “All clear.”