Nicknamed "Die Hard on a Starship" by Trek fans, this action-packed episode features Picard in a one-man battle with terrorists who invade the evacuated Enterprise. Stranded on the ship during a baryon sweep (a space-age decontamination procedure with a deadly beam that combs through the entire ship), Picard plays a ruthless game of cat-and-mouse against a well-stocked platoon, armed with little more than a crossbow and his wits. Data provides comic relief in the hilarious opening scenes as he learns small talk tips from a smarmy and garrulous commander (Glenn Morshower). The two excitedly trade trivialities through a cocktail party ("I had no idea anyone could talk about nothing for so long," exclaims an exasperated Riker), but the comedy soon gives way to one of the most ferocious adventures of the series: Picard takes no prisoners. Future Star Trek: Voyager costar Tim Russ (Tuvok) and Babylon 5 regular Patricia Tallman (also a busy Star Trek: TNG stuntwoman) are among the gunmen.
Trilithium resin is a by-product of exposing dilithium to a matter/antimatter reaction in a warp core.
It is a very explosive material sought after by terrorists to create high-yield explosive devices that leave long-lasting toxicity (TNGepisode"StarshipMine").
In this state, trilithium is a powerful nuclear inhibitor and just a few pounds of the material delivered to the core of a star can trigger a "quantum implosion" of such magnitude that the star will go supernova, destroying anything within the system.
Usually, starships rendezvous with a starbase or with a tanker to refuel before going back to their mission (starships are never designed to be more than two or three years away from Federation space at any time no matter how long their actual mission is).
I admit my recollection of that particular episode is somewhat hazy, but the Bussard collectors can also be used to vent warp plasma, which is perhaps just as explosive as hydrogen and packs a bigger wallop...
There were episodes in VOY in which the Voyager crew had to barter with various alien worlds for warp plasma in order to continue their journey home.