The rescue party can be composed of PCs, rescuing NPCs. Or it can be composed of NPCs, rescuing PCs.

One likely scenario: The PCs go out to rescue some NPCs. Then some NPCs go out to rescue the PCs who have gotten themselves into trouble.

Transcript

GM: Okay Sally, we need you back to translate for the next scene. Here's a note.
{Pilot Zev Senesca flies a hoverplane, searching the icy wastes of Hoth}
Zev Senesca: Aicyż amrof ćyb ot eżom ela, ożud ein. Śoc mam! Ohce azab...
C-3PO: Echo Base... Some meatbag has found some... meatbag-form. Or whatever.
Zev Senesca: Awd Ewiczcuein tsej ot. Awd Ewiczcuein tsej ot. Zsyzsyłs, Acjóbaz-adzaiwg Acdówod. Zsyzsyłs einm yzc, Einatipak Ęknydejop. Awd Ewiczcuein tsej ot.
C-3PO: This is Rogue Two. Captain Solo, do you copy? Starkiller, ditto.
Han: Boy, am I glad to see you guys!
Han: Do you have any firewood?
R2-D2: Wow, Jim. Your plans have reached new heights of non compos mentis.
Han: Thanks!