Meloetta and the Undersea Temple - S15.E48

Ash continues to train at Cynthia's villa until Ridley (a member of an ancient civilisation dedicated to protecting Meloetta) and his Golurk hear Meloetta's song and come to take Meloetta back. At first, Ridley assumes Ash is associated with the thieves, but this turns out not to be the case. Before Ridley can take Meloetta home, Team Rocket assaults the group and capture Meloetta and summon up the ancient Abyssal Temple through its power and song. The heroes try to fend off Team Rocket, but with Giovanni himself present they are too strong.