Once Vergil was set on a path, he wasn't inclined to leave it. Regardless of what others thought, regardless of what it would put him through, he would always complete it unless absolutely forced to do otherwise. And when he was forced, you knew he would remember what had happened and hate whoever or whatever had prevented him from carrying out his plans.
Dante knew the moment Vergil walked out that he would see his brother again, but only once he had found what he was looking for, set in motion whatever plan he might have had. They weren't telepathic, they weren't even particularly good at reading each others faces, but Dante was not stupid and watching his brother stare fixedly at the wall all night had been something of a clue that Vergil was thinking, and thinking hard.
They both had ways of grieving for their mother, Vergil silent and brooding as he read his books, while Dante went on as if life was normal apart from the fact he drank himself into a stupor regularly. He never thanked his brother for always finding him when he had successfully paralysed himself, be it collapsed on their doorstep with a vague knock, or asleep against a toilet's cistern in one of the local bars. Finding him every single time, as if Dante was wired with a homing beacon. He didn't know the homing beacon was in the form of mutual friends, didn't know because Vergil never spoke of it.
And every time Vergil would scrape him up, Dante usually too pissed to fight back or argue with more than a grunt, and take him back home. Gutter dirt, cigarette ash, booze, piss, puke, all of it disappearing in the bath, Vergil not saying a word. He had told Dante once what he thought of the drinking and had been silent ever since, picking up after his brother calmly regardless of how it preyed on his mind. Dante would usually be asleep before he'd been lifted from the bath and carried to his bedroom, laid out on the bed while Vergil threw clothes reeking of God-only knew what into the kitchen on top of his brother's growing pile of undone laundry. Vergil's patience had its limits.
Waking up was always the same ritual; one bucket, three glasses of water, and two paracetamol tablets on the bedside cabinet. Vergil would be sitting in the living room reading a book or browsing using the computer, sliding a sandwich over to Dante; chicken, beef, ham, whichever meat smelt least when he pulled it from the fridge. Dante would mutter vague thanks and use the sandwich to replace whatever had vacated itself into the bucket at his bedside, scratch the back of Vergil's neck with his free hand. If it had been a good week Vergil would lean back against the hand, let himself be scratched. Bad weeks and the hand would be slapped away. A really bad week, and he had enough sense to know any attempt to scratch would get his wrist twisted until it sprained or snapped.
Lately there had been more bad weeks than good, but Dante had been easing up on the drink. He drank when he had to force a happy face, not when he had an excuse for being angry or upset. Paying attention meant realising all Vergil ever seemed to do these days was bury himself in books and research and training, and it was unsettling. Being preoccupied with himself had kept him from noticing the tension that had risen between them, and hadn't given him a clue as to how it was going to work out.
Vergil had been the one to climb on top of Dante, prep himself, and slide onto Dante's cock. It hadn't been a long, arduous decision. Dante had mentioned briefly how he thought his twin's legs were better than any he had seen in porn, Vergil had glared at him, and then they were kissing, deciding human conventions could fuck themselves, and as clothes came off Dante was glad he was enough of a pervert to keep lube in his bedside cabinet.
It was only when Vergil gasped as he came that Dante realised he hadn't heard his brother speak once while he was sober. Not in weeks. Worst of all, he couldn't think of anything to say to Vergil - he couldn't get attention, not with that distracted look in his brother's eyes, and it was maddening. He stroked Vergil's neck, stroked his spine, his side, his hip, nothing would make his brother turn back towards him. Vergil just lay there mute, distracted, looking straight ahead at nothing in particular but all Dante wanted to know was what his brother was seeing. Something had disturbed Vergil, and Dante had been too out of it to notice until it had taken over.
Vergil was dressed by the time Dante woke up and words were exchanged then, making sure Dante knew what pharmacies didn't check the legal limits on buying painkillers, who he could go to if he lost the keys to the house. Menial tasks. He didn't tell Dante where he was going, just smiled a little, eyes not shadowed or secretive, and adjusted his gloves. He said he would not be provoked, and he meant it. Dante hadn't meant to be provoked either, but still ran to the door five minutes after he heard it close, stained boxer shorts barely holding to his hips, and shook with nerves as he realised that Vergil had meant to leave. There had been no hesitation, no clue as to where he was going, and the computer had been wiped twice. His twin knew all too well that Dante would not be able to read into where he was going from their own books, and some of the tomes he had been burying himself in were missing.
Dante knew he'd lost his brother. He just wasn't sure when it happened.