The challenging economics of New York theater makes two-actor plays a holy grail for Off-Broadway producers. Among the numerous two-handers of the past three or four theater seasons, none has had a more arresting first act than Joanna Murray-Smith’s Switzerland. Set in an Alpine aerie, with Cold War elegance courtesy of scenic designer James J. Fenton, Switzerland depicts a showdown between Patricia Highsmith (Patricia J. Scott), author of Strangers on a Train and The Talented Mr. Ripley, and a man she has just met named Edward Ridgeway (Daniel Petzold).