I've manage to run two sessions of Planescape so far:
The group works for the Nightwing Restorations office on Eberron's plane, just outside the city of Sharn. Their manager is Serendipity Dumont, who was crippled several years ago by an assassination attempt.
They headed into the Astral Plane, to an abandoned outpost of the githyanki (all that is left of the body of the dead god the githyanki has settle on is the head) know as Crown. Their goal is to meet up with a rogue modron, named Twonky. They are to escort him back to Eberron.
Aside from a near run in with Twonky's friend, Redgy (a gold dragon) and a verbal barrage with the local boss of the Polian Mining Service, Lingo Maneet (a rakshasha), things go great and Twonky leaves with them.
When they arrive in Eberron (the planar gate is located in the Egress--think Grand Central Station for steampunk trains and air ships), they have three travel options to return to their HQ, known as the Manor: train, limo, or wagon.
The Bard chooses a limo and is attacked by...well...apparently Boba Fett. It appears that the mandalorian isn't looking for the Bard, so he makes it out alive of a thirty "car" pile up on one of Eberron's "interstates".
The Ranger takes the train and is attacked by a group of warforged, known as the Sound of Thunder, mercenaries that work for a man named Fiacho. He manages to fight them off and run away.
The rest of the group look for some additional information about why Twonky's important and find out that in the last 18 months, three other rogue moderns have been murdered and it seems tied to a war brewing between cultists of Law and Chaos in the Outer Planes.
Eventually, everyone makes it to the Manor and checks in with Serendipity. They learn that her client is looking for the Rod of Seven Parts and she has been told that Twonky is a construct to contain a piece.
If the group agrees, she has their next target: a flesh golem named Camilla.
But they have to go the Demiplane of Dread and Desire.
They have to go to Ravenloft and she can't guarantee their return.
After they agree (of course they do), she gives them an elixir to drink and leaves an ancient urn for them to open after she vacates the room.
When the breach the seal of the urn, mists erupt all around them and when the clear, they are on a lonely road in a deep forest with a full moon staring down at them and several figures approaching from the shadows...