The monster hyphotesis

Neil Josten has rules, and the most important one is simple: do not get attached. Not when his mother made it clear that any real relationship could threaten the fragile stability of his new identity. But when a slip in the lab puts his entire future at risk, Neil does something wildly out of character, he proposes a fake relationship to the surly and intimidating professor who accidentally gets tangled in his mess.
Their fake dating is supposed to fix Neil's problems, not multiply them. But the deeper he sinks into Andrew's world, the hunger, the secrets, the pull he is terrified to name, the more obvious it becomes that this arrangement is not safe for either of them.
And when the lies finally unravel, Neil will face consequences far worse than anything he feared, including the possibility that the one person he should never love is the only one he cannot let go.