This happens directly have the opossum attack where Serinth injures herself protecting him. They have all been separated and he awakes to find only Sabriel and Serinth. The concussion he gets her affects him for the rest of Series A and noticeably dampens his personality.
Jagex wakes up in the snow, covered in blood, he can hear Sabriel cursing and making a bunch of noise as she digs through debris. He's suffered a nasty head injury, with a bandage wrapping around his skull and covering an eye. He has some other bandages hastily applied, and he wakes up under a blanket. He sees a lot of red around him and thinks someone must have been seriously hurt with all this blood, then he realizes it's his own blood. When he gets up he immediately wants to lie back down, maybe cry, he feels like his skull was cracked with an axe and he has to take a sharp breath in order to remain standing, he tightens the blanket around him and steps forward, wandering what happened to his armor.
He recognizes Sabriel in front of him digging through the wreckage of the battle, he's swaying as he watches her, he tries to speak but the words come out a jumbled whisper, he swallows a dry sore swallow and tries again.
Jagex (struggling): S-srial...
Sabriel stops and turns back, shocked but also delightfully surprised.
Sabriel: You're awake.
Sabriel (quickly turning back to the digging, sniffing in one spot, then moving and digging again): I should have known [the name of their bloodline] would [recover quickly]. Are you feeling okay?
Jagex (murmuring): Everything's confused...
Sabriel (still digging): That's because you split your head open. Can you move?
Jagex just watches her vacantly and realizes how incredibly thirsty he is. He bends over to try to lick up some snow but ends up toppling over pathetically.
Sabriel ends up tending to him, tightening the blanket and telling him to stay put, but they can't leave yet. He watches her dig until she finally finds what's she's looking for. She pulls Serinth out of the wreckage, she's unconscious, with half of her face missing. Jagex doesn't even recognize who it is at first.