Sleepless in Pre-Battle - S11.E52

The group heads to the Canalave Gym, but they are told that the Gym Leader isn't there right now. At a police station, the group is told by Officer Jenny that all the people in the town are having nightmares, and that the cause of the nightmares seems to be the Pokémon Darkrai. Also, Dawn's Swinub evolves into Piloswine in order to stop Team Rocket from stealing Cresselia.