Short Answer: The boys look for Dally Winston immediately after Johnny kills Bob Sheldon.
In chapter four, a group of Socs attempt to drown Ponyboy in the fountain of a local park, and Johnny saves his life by stabbing and killing one of the Socs holding Pony's head underwater. Immediately after Ponyboy regains consciousness, he begins to panic and frantically asks Johnny what they are going to do. Johnny mentions to Ponyboy that they need money, a gun, and a plan. Johnny then comments that they will be able to attain all three things if they find Dally. Johnny has faith that Dally will help them out and come up with a plan for them to skip town before they are arrested. Johnny and Pony then travel to Buck Merril's place, where Dally gives them a gun, fifty dollars, and valuable advice. He instructs the boys to hop on a train headed towards Windrixville and hide out in an abandoned church on Jay Mountain until things settle down.