Brian, Josefina (or Jo), Chad and Sean (Chad's dad) are one a small sail boat in the Caribbean, when they find the morphing cube. They pass it around before Tarry flys up to them and says that he an Andalite trapped in parrot morph and we all have the power to morph and are threatened by the Yeerks. They don't believe him. So to prove it Jo and Chad acquire a crab and Chad morphs it.
When that get to Galveston, Jo is worried about getting the the cube passed customs. So she takes the initiative and goes first and acquires Olivia a customs agent. She is spotted morphing by Kristen. Chad has the cube in his backpack when Olivia (not Jo he didn't get the hint) and she touches it and... that scene was rather crazy so let's summarize by saying the morphers gained two new members and Olivia acquired Jo.
The Yeerks hear of this odd activity and infest the entire customs office only Olivia runs away with Tarry. She hide in the streets that night by staying in Josefina morph until Sean picks her up and takes her to Houston.
Right now Tarry is chilling in Sean's apartment, while the morphers meet at a coffee shop to talk about the war.