Amusing, I guess.
The PCs are now lv.6 & are in the early stages of CoS. They've had the card reading from the Vistani, they've completed on of the readings & gained an ally - a Vistani who has a way out of Barovia! They also know they are not on the Prime Material & have cut a deal with the ally to get them back there.
So they've arrived in the village of Barrovia late in the day heading to the Eastern gate, intending to leave asap.
They would have tried to leave right then but the Vistani tells them he has some business to conduct at the general store. Suggests they go hang out in the Blood on the Vine tavern, have a drink, & he'll join them in a bit. They take him up on that.
In the tavern they meet Ismaark, win his trust, & learn his sad plight. That after he & his sister (Ireena) bury their father in the morning they're headed as far away as they can get as Ireena's been bitten by a vampire. Their plan is the Abby in Krezk. The PCs though offer to take the pair even further away -
out of Barovia! Afterall, what's further away than another world??
Ismaark tries to keep his voice down & tries to get the PCs to do likewise as there's several Vistani, a hooded man at the far end of the bar, & the barkeep present and he doesn't really want them to overhear.
The PCs are not so careful. Especially one of them. Perception & stealth checks are made. The Vistani overhear but the PCs don't notice.
They also don't realize that the hooded guy was listening in.
The PCs agree to help Ismaark defend his house & sister that night and to help them bury their father at dawn.
Their Visatini ally comes in to get a drink & collect the PCs before leaving. They inform him of the change of plans.
"OK...."
So they go off to Ismaarks to meet Ireena & stand guard all night. They've got a few hours to rest/prep.
Of course the Vistani who were eves dropping on their conversations promptly report this info back to Strahd as soon as the PCs are out of site.
And the hooded guy rides out as well.
They find Ismaark's all boarded up & warded vs vampires. Ismaark tells them (again) that the house has been attacked every night since Ireena's wounds were discovered & that the attacks have become near constant all night long.
As the sun sets they take up their defensive positions..... The PCs guarding various windows/doors, Ismaark, a restrained Ireena (Ismaark knows she's under the vampires influance), & one PC who's player couldn't make it in a bedroom.
This is going to be a combat session of attrition. Survive 12 fights (6pm - 6am), don't let the monsters get to Ireena.
The first 4 fights will be single rolls on the chart of what creatures Strahd has aiding him in an encounter.
The next 4 fights will be 2 rolls per fight on the chart.
The last 4 will be single rolls.
Good luck.
And because the Vistani were able to able to alert Strahd? He gets to makes an appearance to.

I rolled randomly to see wich attack he'd show up in. Attack #4 (9pm).
So they fight some bats. And then some wolves. And Strahd Zombies. Attack 4 is ghouls + Strahd.
Attack 4 leads off with Strahd, polymorphed into a little villager girl, barely "fleeing" a ghoul, beating on the barred door & screaming for help....
I was surprised by what happened next.
This is Barovia. At night. In a house that's specifically warded vs vampires because the problem is a vampire.... With players who're all aware of standard vampire lore.
One PC opens the door, grabs the little girl,
orders her to "get in here!" , and hands her off to a 2nd PC while he takes care of the "pursuing" ghoul.
"Why yes" thinks Strahd, I WILL come in. Thank you very much for the invite.
"
I never thought that ploy would work. I fully expected the players to be like "Oh no, I'm not stupid."
PC#2? Takes little girl Strahd & shoves her into the bedroom with the other NPCs, closes the door & returns to fighting ghouls.
I roll some initiatives for what's going on in the bedroom. Strahd wins. Ismaark & the absent PC fail their saves* & are now charmed etc. (Ireenas already a thrall).
{we play missing PCs as little as possible. They get reduced to modifiers on others attacks/saves etc. So they pass/fail/etc as per whoever they're helping}
Now Strahds just going to have some fun before eventually escaping with his prize.
Over the next several hours/attacks he feeds on Ireena/Ismaark/absent PC, summons monsters to specifically attack the bedroom, gets info out of both charmed & uncharmed characters alike, observes the other PCs in combat action....
Re-upping his polymorph....
Meanwhile the PCs keep failing both in and out of character perception checks to notice things.
Finally, once Strahd had had his fill, he chose to leave with Ireena while the characters were dealing with vampire spawn (the players didn't even wonder why vampires were able to enter the house) & bat swarms.
He jumps out a window clutching Ireena & flies off to his castle on his Nightmare.
The players were utterly surprised by this. While checking on Ismaark & the absent PC (both left alive) one actually asked where the little girl was. He STILL hadn't realized that she was the monster.