It's one of those stories you'd expect in a movie -- a previously-unknown manuscript by a famous author is discovered years after his death. Except that's not the story of the play, it's the story of the discovery of the play. The play was written by Mark Twain in 1898, when he was 60 and broke. It was to have been produced at Bram Stoker's London theater, but the venue burned down and Twain stuck the play in a drawer, where it languished until 2002.
Adapted by David Ives, the play has been modernized somewhat (cut from three acts to two, and tightening the comic screws a bit), but it's still Twain's work, and has a very 19th century feel to it.
The setup is simple: a painter in 1840 France comes to the realization that his work will be worth far more if he has shuffled off his mortal coil. So with the help of a few friends, he fakes his death, and creates a fictional twin sister who handles his estate -- and the millions that come to it now that he is a celebrated (thanks to his demise) artist. Norbert Leo Butz (who was brilliant in "Dirty Rotten Scoundrels") is very funny here -- especially in drag as the twin sister, which is most of the show -- and is ably supported by a cast with serious comic chops.
Just remember that "Is He Dead?" is a very old-fashioned sort of play. There is lots of falling in love, mistaken identities, physical humor -- and very little plausability. It's broad and silly and ludicrous -- and loads of fun.