Kidnapped! Naruto's Hot Spring Adventure! - S2.E97

The group are on their way back to Konoha when they stop at a town with hotsprings. Unknown to them they are being watched by men looking for Tsunade. Naruto's room gets raided and the necklace he was given goes missing with nothing but a ransom note left behind. What does it all mean? Can Naruto get the necklace back and why are they looking for Tsunade in the first place?