In the third season, Sarah's "head" once appeared in a box, received by Lincoln. Perhaps due to the long-standing appeal of many fans, or perhaps due to the crew's consideration from the perspective of ratings, in any case, Sarah, the not-so-common female element in the show, finally returned. Her romance with the male protagonist Michael is obviously something that many fans enjoy watching. Season 4 of Prison Break will provide some explanation for her return, although the explanation may not be perfect. However, the fans probably can't care about this now.
The entire fourth season of Prison Break was filmed in Los Angeles, and the main storyline will be a showdown with the "Company," with the support of the FBI. FBI agent Donald Self offered Michael and Lincoln a deal: form an A-Team, help the government take down the Company, and all past records will be erased, granting the brothers and Sarah complete freedom. Otherwise, they'll have to go back to prison. Clearly, the brothers have no other choice, and other members gradually join this A-Team, including T-Bag, Sucre (Sug), and Bellick (Barryck).