“This is the bit that really sucks: it keeps the human skin. Well, it’s not really human by then—it’s the Cymic replicating human skin—but it looks and feels for all the world like proper flesh. The Cymic merges with human DNA and learns how to imitate its host’s appearance perfectly. Every hair, every scar, everything. Not only that, but it absorbs its host’s memories and knowledge. So it not only looks like it’s human, but sounds and acts like it, too. You see how it could spread so quickly?”

Mitzi’s team all nodded, except for Mir, who bowed her head.

“Yeah. There’s almost no way to tell a Cymic apart from a regular human. Your twin brother could be turned, and, provided he kept up the human appearance, you could go weeks without noticing. It’s the perfect disguise.”

“So how can you tell?” Adam asked.

“Blood.” Mitzi raised her right hand, pulled a penknife out of her pocket, and pressed the tip of the blade to her palm, putting a tiny nick into the flesh. A drop of blood beaded at the cut then ran down towards her wrist. “Cymics keep our skin, but they don’t keep anything else—not our skeletons, our organs, or our blood. If you cut a Cymic, all you’d see inside is black stuff.”

Satisfied that her demonstration had impressed her new crew, Mitzi replaced her blade. She plucked a cloth out of her back pocket and clenched in her fist to cover the cut. “Many stations without Central’s detection software are using that very crude blood test to know which visitors they can trust. They’ll let the crew of a strange ship into their airlock and ask each of them to cut a finger or a palm, to check that they bleed. If the visitors refuse, the station cooks them.”

Adam opened his mouth, and Mitzi nodded before he could speak. “Yes, you were right; they can be killed with fire. Also by extreme heat, electricity, and high doses of neurotoxins. Things that don’t work on them are guns, knives, crushing, pulverising, freezing, starving… or basically anything else that would kill a human. Because the Cymics absorb their host’s DNA, they can repair any damage, no matter how severe, within a few minutes. You can literally turn one into paste, and he’ll piece himself back together in front of your eyes. Fire, neurotoxins, and electricity are really the only things that work against them.”

“Are they hard to kill?”

The question was so quiet that Mitzi thought it might have come from inside her head; then she saw Elle shooting her tentative, anxious glances. Mitzi opened her mouth but hesitated.

They’re your team. They deserve the truth. “Yes.”

Elle nodded, as though that was the answer she’d expected.

“The Cymics have three forms,” Mitzi continued. “There’s the native form, where they’re a large, slimy black monster. In their native form, they’re incredibly fast and strong. The main upside is that they can’t see, smell, or hear you, though they can feel vibrations in the air and through the ground. The second form is the human form. That’s where they’re wearing their host’s skin and look exactly like your neighbour or your sister or your best friend. They’re the most dangerous when they’re in their native form, but they’re hardest to kill in their human form.” Mitzi paused and offered her team a tight smile. “Have any of you ever shot another human at point-blank range?”