Bellamy and Monty meet with Kane and Indra so they can head out in search of Clarke in episode 3x01 "Wanheda: Part 1".
From episode 1x11 "Fruit of the Poisonous Tree".
Amaya, Rory, and Nate head to where the battle between the army and the Dominators is occurring to capture a specimen only to be captured by government agents in episode 2x07 "Invasion!".
Source: Vancity Buzz
Nicole meets with the feds to arrange the release of Ben and his friends in episode 2x07 "Entrapment".