By the time the back of Sui Zhou’s hand starts to swell, skin turning a splotchy, sore red, the young woman who had pressed a kiss to it in thanks has long since disappeared into the crowd.

The good news is that it provides some much-needed confirmation, alongside further clarity: they now know the trick and the twist as to how their current suspect is orchestrating a rather elaborate extortion scheme. The bad news is that Sui Zhou is poisoned.

The good news is that it doesn’t matter that they’ve lost her, since she’ll seek them out soon enough. The bad news is that Sui Zhou is poisoned.

Pei Huai, while berating them half as much for nearly bashing down his clinic door in the middle of the day as for playing bait and switch with a suspect like idiots, ties up his sleeves and sits Sui Zhou down on his table. When Sui Zhou tries to strip off his outer robe, he’s slapped at and tsked, which surprises even Tang Fan, who makes an instinctual noise of protest on his behalf.

“Move as little as you can,” Pei Huai instructs, before turning his glare on Tang Fan. “You! Start moving more!”

Tang Fan strips Sui Zhou down to his inner clothes, but faster, which seems to appease Pei Huai at the same rate it seems to discomfort Sui Zhou. Tang Fan shoots him an apologetic look as he knots a strip of cloth around his bicep, too tight to be comfortable, and Pei Huai starts scraping at the back of Sui Zhou’s hand once they’ve confirmed they haven’t tried to wash it since the kiss.

“This is ingenious,” Pei Huai observes, some long minutes later, as he’s busy distilling what’s left of the poison that hasn’t yet absorbed through the skin down to its base components.

“How can you be so tactless?” Tang Fan retorts, jerking his chin. “Sui Zhou is poisoned, and here you are, praising the method!” It is quite an ingenious method, but still. Has Pei Huai no restraint? Sui Zhou, his patient, has been poisoned. The fact that poisoning, if not any other sort of incident or injury, sees them in Pei Huai's clinic with alarmingly frequent regularity, is entirely beside the point. Some consideration is clearly called for, here.

“You’re right,” Pei Huai concedes, in the distinct tone he uses with Tang Fan to indicate he’s not listening to Tang Fan, before he straightens, spins around, and starts rifling through a case on his desk.

Sui Zhou, for his part in the proceedings, is remaining silent, save for the occasional sharp inhale or shaky exhale that he can’t seem to help as the poison slowly slinks up his arm, licking fire across the span of his skin in its path. The most he’s talked throughout the entire debacle is to let Pei Huai know his symptoms. Tang Fan touches his hand to Sui Zhou’s shoulder gently in reassurance before he’s promptly swept up in Pei Huai’s bustling once again.

“Here,” Pei Huai says to Tang Fan, when he’s already shoved something between his lips. Tang Fan reflexively closes his mouth down around it, then splutters when he realises it’s lip paper. The damage is already done; his lips are stained a bright red when Pei Huai pulls it free and ducks out of reach.

“Ah, ah!” Pei Huai interrupts, staying the objection Tang Fan is opening his mouth to free, “it stops the poison from absorbing!”

"Does it?" Tang Fan freezes, the back of his hand turned towards his pursed lips.

"Yes," Pei Huai confirms, with confidence. Then, quieter, half-coughed, "Possibly."

Tang Fan, though he deflates immediately, doesn’t understand, exactly, why it matters, anyway, not until Pei Huai sets out twelve bowls and starts upending various vials and jars into them in a way that is surely calculated but to the eye looks hectic and haphazard. “Based on the ingredients used, there are twelve possible antidote combinations,” Pei Huai explains when he’s done, dusting his hands as he backs away. When Tang Fan doesn’t move, he gets a look and a raised brow. “Well?”

Oh? “Oh!” Tang Fan remarks in realisation. His face falls, only to rise up again in a belligerent crumple, brow furrowed and eyes narrowed. “Lao Pei, you can’t be serious!”

He tries not to round on Sui Zhou for support, but it’s a near thing. It’s not that he wants Pei Huai to be— the one who administers the antidote in this way, precisely, but, it’s— it’s principle! He’s the physician!

By the time Tang Fan has put himself together, absolutely not stomped over to the table to wet his lips in the first potential antidote, and turned back to Sui Zhou, Sui Zhou’s expression is schooled down to blank focus, slate-wiped and borderline serene.

Tang Fan kneels on the step, does not stall for time by gathering the skirts of his robes up around him, then takes Sui Zhou’s hand between both of his own and presses a kiss to the back of it where the skin is at its reddest and most irritated.

Sui Zhou hisses through his teeth. “Sorry!” Tang Fan stammers. Then, “Any better?”

“It won’t work immediately,” Pei Huai pipes up.

“I know!” Tang Fan snaps.

“It’s not,” Sui Zhou mutters, voice strained. “Any better.”

Tang Fan turns his head and tosses Pei Huai a glare. “Quick, quick, bring the rest over, then." And, to preempt complaint, he adds, reasonably enough, "It takes too much time to walk back and forth with each dose!”

Pei Huai brings himself, two more bowls, a brush, and a damp washcloth over. Between the three of them — the two of them, really, as Sui Zhou’s part to play is to simply sit still and speak up if he starts to feel differently — they manage to expedite the process with the establishment of a system. Pei Huai cycles through the bowls, back and forth between the bed and the table, and helps wipe Tang Fan’s rouged mouth clean of any excess antidote not kissed off onto Sui Zhou’s skin. After a few minutes with no input from Sui Zhou, Tang Fan paints his mouth with a different dose, and kisses him again.

The second last antidote is the charm. Tang Fan allows himself a rather loud sigh of relief when Sui Zhou rasps out that the burning is starting to abate, squeezing Sui Zhou’s fingers absently when he looks up. The skin of his neck and chest are mottled red, but Tang Fan quickly tamps down on the concern that sparks to life behind his ribs and spits up the back of his throat; even if the poison has spread that far up, the antidote will soon follow after it, its own pace made quicker for the removal of the cloth tie and the hasty flex of Sui Zhou’s numbed fingers. By the time their poisoner completes her tail of them and comes by the clinic looking to make a bargain, they’ll be dressed, cleaned up, and ready in wait.