The Greek god Dionysus goes to Hades to resurrect whichever deceased writer wins a battle of word and wit: George Bernard Shaw or William Shakespeare. The American Century Theater stages The Frogs, the only Sondheim musical (book by Burt Shevelove) set in a swimming pool. Jack Marshall directs this hybrid of Greek comedy and classic slapstick by two-thirds of the creators of A Funny Thing Happened on the Way to the Forum.