This episode's headline: Eastern Connection; Chemical Weapons; Small World. ANCHOR: JIM LEHRER; GUESTS: REP. PORTER GOSS, Chairman, House Intelligence Committee; REP. NANCY PELOSI, [D] California; KENNETH LIEBERTHAL, University of Michigan; JEANE KIRKPATRICK, Former U.S. Ambassador to the U.N.; BRENT SCOWCROFT, Former National Security Adviser; CORRESPONDENTS: KWAME HOLMAN; ELIZABETH FARNSWORTH; ROGER ROSENBLATT;