Then she saw it: a fountain. Instead of water it sprayed red blood cells, the flattened lozenges that were never supposed to fly loose in the cranial fluid. The artery lay like some massive fire hose, coiled across the surface of the brain. It pulsed obscenely with every beat of her racing heart and the blood cells twirled as they flew, then arced away, scattering through the liquid.

The enemy was cutting into her artery.

“No!” she cried.

“What?” Keats demanded.

“He’s cut an artery!”

“Where? Where?” Keats grabbed her shoulders, shaking her, forcing her to pay attention and answer.

“Hippocampus,” she said, and Keats sent his biot racing to her.

In Plath’s mind she saw the three open windows. Nothing but glass in one. A bleary view from Anya’s half-closed eye of the other side of Anya’s bed, empty—a slit of light coming from the bathroom. And in the final window that deadly fountain.

She sent her biot racing toward the deadly leak, clambered madly atop the artery and saw her mistake. It was not coming from the artery itself but from a much smaller vein just behind it. Still dangerous, but the pressure was less intense. Still dangerous, still potentially deadly.

And yet, had the foe wanted to kill her, it could certainly have sliced the artery. And there would be more than a few hundred cells flying. He could have done it more than once in the time available. She could right now be swimming through a blood-clouded fluid.

She had nothing to patch the hole. “Bring some fibers,” Plath told Keats.

“Yes,” he said tersely. He still held her shoulders. She shrugged him off, turned away, ashamed of her suspicions, ashamed to have him know.

Veins were delicate things, unlike arteries, which managed higher pressures. This vein was about as big around as the biot—translucent, like a worm that never sees sunlight—and it undulated as the blood cells jostled and pushed to make their way back to the heart.

Then she saw the bulge. Something larger than blood cells almost too large to squeeze through the vein. The enemy. It had not just punctured the vein as a distraction, it had stretched the cut to crawl inside and escape.

She could stab it right through the sausage-casing walls of the vein. She could probably kill it. But she’d be poking holes in her own vein, and the enemy—who had thus far not done anything as drastic as cut an artery—might get frantic, might start slashing from inside the vein.

“I’m almost there,” Keats said.

“I’m going after him,” she said, without explaining what she meant.

With her front two biot legs she pried open the elastic flesh of the vein. Blood cells pummeled her face. A white blood cell hit her, rolled down her back, and clung on. It took all her strength to push into the flow, like trying to move uphill against a rockslide.

Halfway in and the pressure shifted. Now it was cells in the vein battering her like dozens of flat stones, pushing her head and upper body after the escaping enemy. She slipped the rest of the way in and fought down the claustrophobia as the vein fitted around her like a body sock. The blood was pushing her along, pushing her toward the distant lungs where oxygen would flow to the cells and they would be fired into arteries for the outward-bound trip.

She could see nothing but blood cells, red and white, crowded all around her. Her hope was that her prey would soon cut his way out and she would be swept along with him.

But if he didn’t? If he rode this all the way to the heart and the lungs? She could be lost forever in the miles and miles of blood vessels.

“No!” she said in sudden panic.

“I don’t see you yet,” Keats said. He had switched on the harsh overhead light so that the two of them, in various states of dress, looked sickly and frightened.

Too late to get back to her entry point, Plath knew; now she would have to cut her own way out. A second bleeder in her brain. God, she was making things worse. A risk of a second blowout that could kill her, weighed against the terror of being lost forever inside her own body.

Soon this vein would merge with another, and then any exit would cause more blood loss. She had to cut her way out now or lose her chance altogether.

She stabbed a claw into the vein wall but almost could not hold on against the pressure. Making matters worse, the cell was on her back, oozing its way like warmed Silly Putty into her shoulders, reducing the mobility of her legs. And another now attached to her left hind leg, a fat slug of a thing wrapping its mindless self around her sticklike limb.

Panic!

She slashed madly at the vein wall, heedless, cut it and felt the blood change speed and direction. Biots are not flexible, so all she could do was use her front legs to cantilever her rear out of the incision.

Suddenly the pressure was too much. Her grip failed. Her biot went tumbling end over end, no way to tell where she was, in or out of the vein.

And then, all at once, she was floating free in cerebral fluid, riding like a beach ball atop a stream of cells. She grabbed onto brain tissue and hauled herself out of the current.

From there at last she could turn around and see the damage she’d done.

The leak was twice as large as the first one. Cells were flying out in threes and fours rather than singly.

With her heart in her throat she grabbed Keats’s shoulder.

“Where are you?” she demanded.

Keats took her in his arms and held her as his biot crossed into view bearing a half-dozen fibers to begin the job of yet again saving Sadie McLure from her own blood.