Raduin711
Hero
I think that there isn't necessarily 1 plan of action for a paladin, because there is more than 1 way for a LG person to behave.
Letting the Imp go could be considered the right thing to do because he would be keeping a promise; even if it wasn't one he himself made, he could consider himself honor-bound to leave the imp be by virtue of belonging to the group.
Killing the Imp could be considered the right thing to do because the Imp has hidden himself from the paladin's sight until that moment; allowing him the item in question could be considered the same as associating with that Imp, which a paladin cannot do. This revelation could be seen as an indication that the Imp means to do evil with the treasure.
I wouldn't concern myself too much with the paladin's actions.
Letting the Imp go could be considered the right thing to do because he would be keeping a promise; even if it wasn't one he himself made, he could consider himself honor-bound to leave the imp be by virtue of belonging to the group.
Killing the Imp could be considered the right thing to do because the Imp has hidden himself from the paladin's sight until that moment; allowing him the item in question could be considered the same as associating with that Imp, which a paladin cannot do. This revelation could be seen as an indication that the Imp means to do evil with the treasure.
I wouldn't concern myself too much with the paladin's actions.