Rey and Finn are trying to retrieve Luke Skywalker’s lightsaber from an enemy spaceship
They sneak their way into the armory and discover over a hundred lightsabers piled up.
They don’t have much time as the guards could catch them any minute, and they have no idea which saber is the one they’re looking for.
Quickly, Rey grabbed one saber, tossed it away, another one, then another, and until after a dozen sabers she holds onto one like she’s sure she’s found the one and proceed to run towards the exit.
Once they escape, Finn asks her how she was so sure earlier about that lightsaber being the one.
“It’s the only one that was… Lukewarm”, she replies.