Episode 7x15 is titled, "Something They Need." The official synopsis for Something They Need reads, "A group of Alexandrians embarks on a journey to a distant community. One group member must make a heartbreaking decision."
The journey in reference is to the Oceanside community which was introduced in Episode 7x06 (Swear). The Tara-centric hour introduced a group of women whose men were killed by Negan and the Saviors but also happened to have a massive cache of guns. Before the hour concluded, Heath had gone missing but Tara made a promise to never tell her group about this community.
Two weeks ago, Tara was last seen breaking that promise as she pulled Rick aside in Alexandria to tell him about the community as Alexandria needs guns to satisfy Jadis and their new allies in the war against Negan.
As for which character will have to "make a heartbreaking decision," there are a number of possibilities. Last seen rushing into the Sanctuary on a suicide mission, Sasha appears to be captured and might be forced to make a difficult choice by Negan, while the dark possibility of Eugene having to kill her to prove his allegiance also exists. Of course, Rosita also encountered a mystery man who many suspect to be Dwight of the Saviors. Perhaps their encounter will lead to some sort of a "heartbreaking" decision.
Tara, however, might be the character in question, as breaking her promise to the Oceanside community and her friend who saved her life will likely pile a bit of guilt onto her conscience.
Either way, we will find out on Sunday night as The Walking Dead airs its penultimate episode of Season 7 and sets up a sure-to-be explosive finale.
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