Luo Binghe experiences curse-induced amnesia after he escapes from the Endless Abyss.
The last thing he remembers is the attack on the Immortal Alliance Conference, and Shizun coming to help fend off the Ghosthead Spiders, but everything after... it's too foggy, he gets the strong sense that something bad happened, and that actually a lot of time has passed, but the particulars elude him.
Anyway, Binghe realizes that he's in the demon realms and that he's somehow gotten his hands on a very cursed-feeling sword. He uses the sword to help himself directly escape, then dutifully seals it, and of course he realizes that his demonic powers are a lot stronger. At some point his seal must have broken. He feels a spike of anxiety over it, over the prospect of being caught, but he quickly realizes that even without the seal, he can hide and subdue his demonic traits himself. His training with Meng Mo must have paid off.
Speaking of, the old Dream Demon has been suppressed to where Luo Binghe no longer has to hear his constant commentary any more. Thankfully. Binghe has to dig him out himself to ask if he remembers what Binghe's forgotten, but while Meng Mo can identify that some kind of dark miasma is occluding things, he can't remember either. He speculates that they might have been exposed to something from the Endless Abyss during the attack on the Conference, as that place is known to have a lot of creatures that feed off of memories. Part of its function as a prison entails disorienting the inhabitants, and since the gods abandoned it, many new horrors have mutated from that original purpose.
Luo Binghe hazards a guess that such a creature might have appeared, and in the course of tangling with it, he somehow was dragged to the demon realms. He must have grabbed a demonic weapon to help himself defeat it. But what happened to Shizun? Binghe knows himself well enough to know that only a few things can provoke him to recklessness. If Shizun was hurt...
Well, there's an obvious way to find out. Binghe returns to Qing Jing Peak, where he's subjected to a stunned reception, before being hurried right to his master. Ning Yingying tearfully explains that everyone was sure that he had died during the demon attack. Ming Fan even tests him to make sure he's not some sort of walking corpse or illusion! They find Shizun at a sword mound, at a sword mound for Binghe, and indeed when he first sees him, Shen Qingqiu looks like he's seen a ghost.
Shizun seems... hesitant. Suspicious, maybe, but of course he's less overt about it than Ming Fan. He doesn't look well. Luo Binghe prostrates himself to beg for forgiveness, and after a moment that feels almost too long, Shizun bids him get up and explain himself. Haltingly, Luo Binghe admits that he has lost most of his memory, and as such cannot explain everything even to himself.
For a while it seems almost like Shizun thinks he's lying about his amnesia, although Binghe cannot fathom why he would lie about such a thing. It would be a lot easier if he did remember! Then he could explain why he's apparently been missing for more than an entire year!
But gradually the suspicion fades, and things settle more or less back to their normal routine.
The other peak lords come by. Yue Qingyuan shows up within the hour of Luo Binghe's return, and is waiting outside when Binghe emerges with Shizun. Then Wei Qingwei and his demon-detecting sword show up (luckily, Binghe's control seems sufficient that the sword remains sheathed). Qi Qingqi, Mu Qingfang, and even Shang Qinghua all stop by, incredulous and fascinated and bug-eyed with disbelief in turn. Liu Qingge is off killing something, but he cuts his mission short when a messenger finally catches up to him, and returns early to glare accusingly at Luo Binghe and practically dog his heels for a week.
Everyone seems upset with Binghe, and Binghe feels upset right back at them. Just look at the state his master is in! What have they all been doing?!
Binghe's room is untouched from how he left it before the conference, apart from a few new layers of dust. He sets about cleaning and airing it out, and then immediately launches into a rigorous plan to rebuild his master's health. On the one hand, he is deeply touched that Shizun grieved him so much that he was wasting away. On the other hand, it's absolutely unacceptable for Shizun to actually waste away!
At first Shizun remains in bad condition. He hesitates over large meals, though he can be coaxed to eat simple foods, and his sleep is fitful and often incomplete. Sometimes he stares at Luo Binghe in ways that feel unnerving, and other times he looks near to tears as he brushes Binghe's hair and lets slip the occasional exclamation of relief, or reference to white lotus flowers.
Eventually, these moments become more infrequent. Shizun resumes eating regular meals, and helps find a suitable place to store the sealed demonic sword, and arranges for Luo Binghe to revisit Wan Jian's sword hall. He no longer sends Binghe on many missions, but that's fine, as Binghe doesn't want to go on them alone anyway. His sleep becomes more consistent and restful. His flares of Without-a-Cure become less frequent too, and his cultivation heals from the neglectful damage that was done during his turmoil.
Huan Hua Palace goes on the attack, producing allegations of Shizun's misconduct, some woman comes out to claim to be his fiancee, the sower demons claim he was aiding them, and the Palace Master accuses Luo Binghe himself of being the hidden son of Tianlang Jun and whips out an artifact that reveals his demon side.
In the process it also somehow breaks the curse on him and Meng Mo and restores aaaall of Binghe's lost memories.