Silas and Oak had been bunking together, well, since Oak started working at the ranch. At first, Oak wasn't unlike a particularly feral barn cat. Any attempts to be friendly made by Silas would be immediately snubbed. Oak would not talk to him unless his work for the day required it, and he would turn in early, immediately after dinner was finished.
Eventually, Oak began to open up to Silas. Oak lets his "silent and mean" act slip after someone gives him stupid instructions on how to complete a routine task, and Oak couldn't help but to talk back, mocking them under his breath, not realizing that Silas was totally within earshot. With the shock of hearing Oak say something for the first time that wasn't just two words, /and/ having heard Oak say one of the funniest things he's heard in a long time, Silas immediately busts out in a sudden bark of laughter. Oak whips around towards Silas, face completely red with embarrassment. The person who gave the instructions also turns around at the sound. They ask Silas what was so funny as Oak looks at Silas, embarrassed and upset at what he believes is Silas' imminent betrayal. But without even looking back at oak, Silas instead covers for him, telling the person who gave the instructions how they've never done it that way at the ranch, and that clearly they've never handled that kind of animal before. Person gets angry/embarrassed, and Silas gets in trouble in Oak’s stead. Silas is out late doing extra work and misses dinner, but upon returning to their room, there is a small bundle of food wrapped up and sitting on his bunk. (Silas immediately thanking Oak vs Silas playing it off vs Silas thanking no one in particular)
Oak starts hanging around Silas more and more often after that, at first just following him around (badly), then Oak making little aside comments a little bit louder and a little closer to Silas to try and get Silas to laugh like that again.
By the time Oak's sisters make it to the ranch, Oak is almost completely out of his shell. He vouches for them and their usefulness for Connor, but the act of them showing up does drive Oak back into his shell temporarily. Maybe Silas witnesses an Oak vs Ash yelling match which is almost entirely Ash just yelling at Oak. Silas almost steps in, but ends up being stopped by Moss. She kind of gives him the rundown of what both of her siblings might be feeling at the moment (which ends up being scarily accurate) and why that means that Silas should let them both get it all out. Moss helps Silas sneak off by revealing herself to her siblings when Silas makes a noise while trying to leave quietly. Later that night, Silas is "woken up" by Oak sneaking into the room. Oaks' eyes are completely red from crying, and his nose is running horribly. Silas is still laying down in bed when he meets Oak’s eyes. There's a split second where Silas is unsure about what to do here--every fiber of his being knows that offering any kind of comfort will drive Oak away like it has in the past. But Silas also knows that flipping over and pretending to be asleep might do something truly irreparable to whatever bond is between them. So Silas reaches out towards him. And Oak lets himself crumble and to truly give into the comfort of another person for the first time since his brother died.
Oak closes himself off again after the first lightning strike. Silas asks Oak if he's okay after Oak stumbles in through the window at truly some ungodly hour of the night looking like absolute garbage, just to have Oak shrug him off. The first day/night after the incident, Silas watches the difficulty Oak is having--he sees the shakiness in Oak’s movements, how unfocused and foggy Oak feels compared to normal. He watches Oak try to hold it together and pretend that he's fine in front of others, and in front of him as well, although to a lesser degree. Oak lies to Silas that he is just sore, or that he pulled something weird, and Silas pretends to not watch Oak struggle immensely to climb into his bunk that night. After Oak heads out the next day, Silas switches bunks with Oak, making sure to be in the room and in his new bunk before Oak can complain about it. Oak almost breaks at the gesture, and /almost/ confides in Silas, but decides against it at the last moment. Silas does not push about it. He knows that Oak will come to him when he's ready.
But Oak never gets the chance. Stubborn and eager to earn redemption for his hurt pride, Oak attempts to go back to his side job. Silas watches Oak sneak out that night, half asleep and thinking nothing of it. A part of him is almost glad to see Oak leave, that Oak is feeling good enough again to do whatever he does. But when Silas wakes up the next morning to a distinct lack of Oak in the room, he feels a little lost. He ends up shaking the feeling off. Oak had left before, and he'd come back before, so Silas had confidence that Oak would come back soon. But when Silas gets home for the day and Oak’s belongings are newly missing, he truly gets worried.
And so Silas, along with Oak’s sisters, Connor, and a few other people, go looking for Oak. Ash makes an offhand comment about how her idiot of a brother is sure good at not being followed when he doesn't want to be followed, and Moss tries to lighten the mood by saying that they've always found him eventually! They search for a week, maybe, with less and less people helping to search each day, until it's just Silas, Ash, Moss, and Connor. Silas gets separated, maybe chasing something that just had a flash of Oak’s silver hair, leaving Oak’s sisters fully in the dust. But when Silas reaches a clearing, he realizes that he doesn't even know what he was chasing--only that he's all alone, and doesn't even know what direction he came from.