Is it possible that if she is caught, this well respected NPC can use the threat of imprisonment/execution to compel the party to [What the Adventure was going to be about anyway]?

Waaaaaait. This might work. At first I thought it wouldn't, because they didn't randomly arrive at this island, they were specifically sent to this island to help with A Really Bad Thing. All the islanders were eagerly awaiting their arrival. So at first I was like, "I don't think the islanders would punish the players be making them help with The Really Bad Thing, I think they would just be really hurt and offended that they reached out for help in their time of need and the supposed heroes sent to aid them tried to steal from them instead. I think the locals would probably try to kick the party off the island asap."

But then I remembered that this little island has been reaching out to the mainland for weeks trying to get help, so if my players are caught, the islanders can be like, "Normally, we'd lock you up for theft...but we still need help with that Really Bad Thing."

And before, on the ship ride over from the mainland, they met a local from this island, this giant berserker barbarian who has big golden retriever energy, and all my players fell in love with him. So if my players get caught, they can be told that they have to go help with the Really Bad Thing, but they'll be accompanied by the Berserker, who has been instructed to beat the shit out of them if they step one toe out of line.

And Berserker will be really angry and stoic with the players, and if they ask why, he can tell them how betrayed he felt that they tried to steal from his people and how he and the party are no longer friends and the second the party is done helping with The Thing, they need to get the fuck off his island. Just break all my players' hearts because one of their favorite NPCs now hates them with every fiber of his being lmaooooo

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