Warning: The following contains SPOILERS for The Book of Boba Fett, episode 4, "The Gathering Storm."
In The Book of Boba Fett episode 4, an extended flashback scene sheds light on the relationship between Boba Fett and Fennec Shand—but why does the master assassin stick around after their business had concluded? The episode reveals how Shand (Ming-Na Wen) survives the events of The Mandalorian episode 5, "The Gunslinger," in which she's mortally wounded in the Tatooine desert. Fett (Temuera Morrison) finds her and immediately takes her to a Modifier (played by Stephen "Thundercat" Bruner, former bassist for Suicidal Tendencies and soundtrack composer for multiple works including Lovecraft Country and Venom: Let There Be Carnage). Shand, completely unaware of this process, wakes up alarmed with her new cyborg torso, laying by a fire with the bounty hunter whom she originally thought was dead.
As surprising as it is to wake up next to Fett, Shand immediately recognizes the debt she owes him for him saving her life. Fett tells Shand about his mission to rescue his iconic ship from Jabba's palace, which at the time was under the rule of Bib Fortuna. Shand agrees, stating that doing so will repay the debt she owes him. Fett, responding indifferently to this proposal, later offers to drop her off after the successful rescue of his Firespray ship, but Shand surprisingly responds, "I'll go for the ride." From there on out, Shand becomes Fett's right-hand woman. However, she doesn't explicitly express why she decides to stay with Fett after the rescue mission.
Boba Fett, becoming more like Han Solo with his choice to reinvent himself after life-changing events, decides to stop working for crime lords by becoming a crime lord himself, and offers Fennec Shand a position by his side in exchange for loyalty and security. Even though Shand expresses her doubts about the otherwise tempting idea, saying that she's an "independent contractor" who values her freedom, it's perhaps the ship-rescuing mission with Boba Fett that changes her mind. In addition, she still technically has a bounty over her head and still owes her life to Fett, despite saying that the ship mission would be a sufficient enough debt repayment.
"Life debts" are taken seriously in the Star Wars universe. Boba Fett stayed with the Tuskens likely for years after they rescued him from the Tatooine desert. Although they captured him as their prisoner, they still saved his life. In return, Fett took measures to defend the Tusken tribe who treated him as one of their own. It's also a life debt to Han Solo that makes Chewbacca his Millennium Falcon co-pilot. A life debt, in addition to their first successful mission together, Boba's exceedingly rare promise of loyalty, and the fact that she truly has nowhere else to go, is why Fennec Shand ultimately chooses to stay. Finally, Boba Fett's Mandalorian implication at the end of episode 4 likely means more muscle to help Fett's cause, which also strengthens the power Shand will have by his side.
Out in the desert, Fennec Shand is still prone to active bounty hunters looking to collect the price on her head, if they find that she's alive. Even if she wants her freedom to be an independent contractor, she'll always be on the run unless she stays with Boba Fett, or somehow manages to clear her own name. Living out a life debt in his servitude is then really her best option at having any security. Fennec Shand is proving to be a strong supporting character in The Book of Boba Fett, with her place by Lord Fett's side becoming more influential with each episode.
The Book of Boba Fett releases new episodes Wednesdays on Disney+.
