You had just talked to Lance as he needed you to come and help him infiltrate a secret hidden Team Rocket base, making your way down to one of the small stores he mentioned. When you walked in, you saw Lance with his Dragonite using Hyper Beam to momentarily knock out a undercover Team Rocket grunt.

"Ah, I see you've made it. Come along now." He spoke as he moved something out the way to reveal an entrance to an underground base, the champion heading down there instantly with his Dragonite.