This episode of The MacNeil/Lehrer NewsHour looks at the following major stories: a look back on the JFK assassination 20 years later, a debate over a new rule by OSHA protecting workers from hazardous chemicals, and a profile on a remote art museum in the town of Marfa, Texas. These major stories are complemented by reports on a go-or-die ultimatum to Yasser Arafat, and a vote in the West German Parliament on nuclear missiles.