A wet, smacking burst, not loud enough to be an explosion, sounds from the back of the Mobile Unit. It is the soft thup of a thick wrestler's loogie being propelled through a rolled-up tongue. It is the distant, muffled splurt of a baby having a big one. Y.T.'s hand, still gripping the bars of the gate, stings for a moment, then feels cold and hot at the same time. She can barely move it. She smells vinyl.