P.L.O. Chairman Yasser Arafat made a conciliatory -- and politically risky -- gesture, ordering the arrests of 300 Islamic Hamas activists, supporters of the militant group threatening to kill a young Israeli soldier by tomorrow if 200 Palestinian prisoners aren't freed. The move, in fact, brought threats from a top Islamic leader whose own house was raided. He said the crackdown would only spur further attacks on Israelis. Rabin, unmoved by the display, threatened to halt the Palestinian autonomy process entirely and even send a strike force into Gaza if Arafat can't save the hostage; whether his life will be saved is now a near unanimous focal point for Israeli fear and anger.