Act I - The Castle

Scene 1 – Meeting up
The TARDIS crew are happily travelling in time when a powerful force grabs the time machine. The vehicle spins out of control as if being sucked into some temporal whirlpool. Explosions spark all over the control room and the crew need to hang on for dear life. Eventually, more with a whimper than a bang the TARDIS lands, crashing silently into a normal looking suburban street. It is night, and the scanner reads a normal American street in very early 21st centaury California. The TARDIS is stuck in Sunnydale.

There are a variety of odd energy readings, but mostly things are fine. However, the crash has damaged the TARDIS, it has blown out its temporal impedance modulator. The part is a very simple circuit, but only if you are a time traveller. There is no way this planet or time has one of these devices, and without it the TARDIS can travel in space, but not time. Luckily the Doctor may be able to build a new device from scratch, but he will need a long list of materials and time. The crew should decide to take to the streets to find what they need and track the source of the temporal disturbance.

The scoobie gang are wandering around on a pretty ordinary night. Depending on the characters you are using, they are walking the streets for these reasons:

Buffy is on patrol as usual.
Willow is walking with her for company, but also because she really needs to talk to her best friend about her break up with Tara. Buffy is hoping Willow will open up as she is worried about her friend.
Spike has been trailing around after Buffy as usual. Just as Willow starts to get talking about things he turns up. He says he just happened to be going past, but Buffy has been able to smell his distinctive cigarettes for the last three blocks.

If you are using the other four secondary characters, they can be brought in like this:

Xander has been sent out for more wedding stationary. He knows the shops are all shut, but it is easier to leave than try arguing with Anya in Bridezilla mode. He is trying not to go home, and is also wondering if she will believe he got the stationary, but it was eaten by a paper eating demon. He spots Buffy and Willow and wanders over in the desperate hope a demon will attack and he’ll have an excuse not to go home.
Anya meanwhile has become frantic. She must have the stationary and has taken to the streets to find Xander. She is also worried something has happened to him, but will be less worried if he is empty-handed.
Tara has been shopping for groceries. She may run into one of the others, and is secretly hoping (and dreading) she will also run into Willow. In fact she happens to be walking home past one of Buffy’s patrol routes as coincidently as Spike is.
Dawn is bored at home. No one seems to stay around her for more than five minutes these days. So she takes to the streets. She is hoping to run into Buffy or someone who can spend some time with her. However, if she is attacked by demons (or just stays out too late) then she may get some of that attention by making Buffy worry.
Note that if they are not being played, Xander and Anya are at home or the Magic Box making wedding plans and Tara is at Buffy’s house looking after Dawn.

When the Buffy group are together, they are attacked by a Sash’Nak demon (or possibly 2 or 3). It is more puzzled than aggressive, but will quickly decide to kill the entire group. The sounds of demonic or human screams will attract the TARDIS crew and join both groups together.

When the demon is defeated, research will identify it as a Sash’nak demon. However, it will also reveal that this form of demon has been extinct for thousands of years.

The Doctor will be able to feel that time is ‘wrong’ here. There is a definite distortion field or a rift over Sunnydale. However, he is unable to locate the source as another effect is masking it.

Scene 2 – Oh look, there’s a Castle
While they are talking, everyone will notice a large castle fading in and out of view. It is on the edge of Sunnydale and looks out of place to even the non-residents. The castle is a sort of medieval design, and quite massive, but has an architecture that is distinctly inhuman.

A power in the castle is interfering with the Doctor’s scans, it could be the source is the castle, but if it isn’t, forces inside it are making it hard to see the real centre of the time rift.

The Castle is full of Sash’Nark demons, troops massing for a great battle. A good few are going out into Sunnydale in patrols to begin some form of conquest. Getting close without being noticed will be hard, but not impossible.
Luckily, if the characters are spotted, most of the demons are still out of phase with local time and insubstantial to the characters. However, this isn’t all the time and they can occasionally make contact.

The castle is the home of an ancient HellGod called Betryal. He ruled this area of the earth in the days of the true demons, thousands of years ago. The time rift is phasing the ancient castle and its occupants into present day. Betryal has seen a whole new place to conquer, and is using his sorcerous Pasha demon servants and his own powerful will to stabilise the castle in this new reality.
He doesn’t quite understand what is going on, but he figures he’ll work that out when he has conquered everything.

Inside, the castle is very Spartan. It is built of white marble in an Arabian style. Betryal sits on a huge throne in the centre of the place. He will probably detect the characters are soon as they enter and draw them to him to discover who they are. He can swat them like flies, but he is more interested in finding out the weaknesses of his enemies. Even better, these interlopers may be able to help his Pasha demons stabilise the rift. Players will have to do some fast talking, as Betryal is not going to shed many tears if they become annoying and he has to kill a few. Unlike his guards, Betrayal can see and interact with the group. (he is a God!)

Scene 3 – Spelling Bee
However things go with Betryal, the players really need to find the Pasha demons and disrupt their spell.

The Pasha are in a nearby basement room working their magic. There are seven or so demons, all chanting and building power. They have four local Sunnydale residents tied up hanging from the ceiling, who they will sacrifice to complete the spell when they have generated the correct energies.

The players will have to fight the Pasha to stop them killing the sacrifices. The Pasha are all armed with Knives and are happy to blast magical lightning at any attackers too (but Willow or Tara may be able to protect people from that).

If the Pasha are defeated the spell they have started must be cancelled. This takes a small ritual using the hearts of three of the Pasha demons. If the players have taken too long or made too much noise, there may be corporeal Sash’Nak demons on the way.

Once the spell is dispersed, the Doctor can get a clear reading on the centre of the rift. If the group can escape the cattle, they may want to go there.