An experimenting Cleric/Mage has opened a portal to another realm. Accidently this corresponded with an experiment in a modern-day underground military base which is performing a physics experiment on time/space. A trans-Time/dimensional portal is formed, both attuned to each other such that neither can be closed until both are closed simultaneously. Meanwhile, a military scouting party of Rambo types have passed through and are exploring the AD&D area (walky talkies, hand grenades, sub-machine guns and pistols, hand-to-hand combat etc). They don't believe what they've ended up in (save vs illusions and mind- affecting spells at +4) and are taking prisoners of anyone who can give information on the situation.
Problem 1: Stop the scouting party (including retrieving their gear if possible).
Problem 2: Find what equipment is needed to close both portals simultaneously - sages can probably help with this - and get the required equipment. (I used a Redeye missile and Staff of power, both of which were in the possession of a Barghest on the plane of Gehenna).
Problem 3: Go through the portal to the Underground base, find the source controlling the portal, and get control of the area. The guards are the (US ?) army equiped with modern gear, but the primary security structure is to block access to the experimental area, rather than the area itself.
Problem 4: Destroy both portals simultaneously. For example, fire the missile into controlling computer complex, while simultaneously breaking (retributive strike) the Staff of Power at the fantasy-side entrance to the portal. Then get the surviving PC's from the underground base to their home realm (either use plane shifting magic or have a time delay on the portal destruction).