It starts innocently, which Melissa later will realize is the exact condition by which most disasters are made.
Rex almost causally comments one day that he almost misses the assault on his mind when she mindcasted on him in full effect. When prompted further, he elaborates.
"I miss the vulnerability we had to each other, Melissa. Now I'm a monster and you're so... controlled that I just can't stand it. I miss you knowing my thoughts before I knew them, I miss you being the one in control."
Melissa gives Rex a funny look before responding. "Things changed, Rex."
They don't bring it up again for several months, not until Midnight travels to Dallas and Rex is forced to follow their crew into a city full of new metals and modernity and a bitter taste in his mouth. Melissa often finds him pacing the room during the time they arbitrarily designate as their "night" time and time to sleep. He tastes disorganized and angry all the time, and Melissa's tired of blocking his thoughts because it is the "right" thing to do.
One night she finally gives in, pulling him down into bed and stripping his shirt off to have maximal exposure of his skin, of his vulnerability. "Fine, Rex. If you can't control your thoughts, I certainly can."
Rex looks relieved for just a moment before the intense nausea hits, the sickening feeling of her sifting through too many thoughts at once. Within three minutes he's leaning over the bed throwing up, and he's pretty sure he's begged her to stop somewhere in between, but the pain doesn't stop and her creeping fingers into his thoughts don't either. He's so exhausted that its a wonder to Melissa he hasn't collapsed yet when she counts off the fifth minute and lets go.
Rex's skin feels like it is crawling when Melissa holds him afterwards, wrapping him in a sheet to prevent even unintentional touching. He shakes for a few minutes and Melissa wonders if she hasn't gone to far like she did when they were younger.
Rex speaks. "Not so hard, Cowgirl. But do it again."
Melissa stares at him in shock. "I was doing that to discourage you, Loverboy. You're not supposed to ask for more."
"It feels... better."
"I can make it feel better forever, Rex. We don't have to do this. I can change your mind, fix some of it."
"NO!" Rex yells, startling the quiet in the room and making Melissa jump back.
"Why, Rex? I don't want to hurt you, I was angry and shouldn't have taken it out on you."
"You didn't rip through my mind, Melissa. It... stopped the thoughts."
"But I can stop them forever."
Rex groans. "They don't want to die, Cowgirl. I don't want to die, and the Darkling part of me is still part of me. I can't want to die. Think of it like a temporary break from the insanity in my own head. You turn up the volume so high I can't hear a thing."
Melissa can't resist an open mind, hasn't been able to since she ran out in her cowboy Pjs to save Rex from his father's darkness.
They only kiss to let Melissa in his mind, now, and they've never had sex because Rex is pretty sure that one of them would end up dead if they tried. But Melissa learns how to give Rex just enough invasion in his head, which thoughts to soften but never to take away. She learns how to respond to his pleading and screaming as they work, like its a special language only they speak.
She learns not to think about the fact that this is just fucking weird, even weirder than normal for them. She's pretty sure this would be called severe abuse if he weren't so enthusiastic in his continued consent.
She grows to want more, as she learns more of his brain and desires, as she becomes an expert in his mind. One day, after a long session and hours spent curled into each other as Rex recovers in his sleep, Melissa finds the words to describe her growing desires.
"I want your body, Loverboy. Not like other people do, but like we do. I want to control your body like I hold your mind in my fingertips. I want your life at my fingertips."
The Darkling in Rex tells him to run, to protect himself. The human in Rex craves more of her touch, more of this game that they're playing that he doesn't know how to justify. He grabs both of her hands and places them on his own neck. He forces himself not to run, to let Melissa send calm thoughts to quiet his Darkling side for just a little while and let his human side feel and enjoy this.
Melissa squeezes, his Darkling screams in his head no matter how much Melissa suppresses it, and Rex is pretty sure that it isn't working. As soon as the thought passes through his mind, a switch flips (one Rex will later recognize as oxygen deprivation) and he fades into her touch, fades into Melissa.
Melissa loosens her grip and Rex gasps. They both ignore the fact that he is obviously physically aroused, because this isn't that and it can't be that. Rex nods at her once he's recovered his breath, whispering. "More, Cowgirl."
And Melissa does, because for some reason only the universe knows, they both want the same crazy things from each other. Melissa squeezes and basks in his terror of death yet again, because it feels good and because they can.