Jennie is the story of the indomitable Jennie Malone (Mary Martin) barnstorming at the turn of the century with her profligate actor-impresario of a husband, James O'Connor (George Wallace), their two children (Brian Chapin and Connie Scott) and his "mellerdrama" troupe of hapless players. Once again the troupe has fallen on evil days. Their latest bloodcurdling production is a success but their spectacular on-stage waterfall has flooded and ruined the theater. Unable to prevent the sheriff from seizing all their luggage, scenery, etc., Jennie finds herself backstage consoling husband James - Waitin' For The Evening Train. In the town square, meanwhile, the stranded actors reminisce as Abe, the company manager (Jack De Lon), sings When You're Far Away From New York Town. Having "taken a stroll" with an adoring local beauty, husband James is rescued from the vengeance of the girl's brother and friends by umbrella-wielding Jennie who forgives him with I Still Look At You That Way. But, disconsolate, James asks Jennie to take the children and leave him.

Enter Christopher
She settles in a New York brownstone with her mother, Nellie (Ethel Shutta), who sings For Better Or Worse to her. Destiny smiles and Jennie wins a bit part in a new play by an English playwright, Christopher Lawrence Cromwell (Robin Bailey) - Born Again. Suddenly she encounters the playwright outside the theater. They sing Over Here, romance seems to blossom and Jennie at home later sings Before I Kiss The World Goodbye. Weeks later at a party at Christopher's town house, following a spectacular comic dance by the ensemble Sauce Diable, Christopher sings Where You Are to Jennie. Later, having at long last arranged for a Sunday afternoon meeting between Christopher and her mother and kids, Jennie is bowled over by the sudden return from Seattle of husband James - See Seattle.

Act II finds the reconciled Jennie and James, children, Irish mother Nellie, and touring company in a dilapidated ex-church in Seattle which James plans as a theater. To lift their spirits, Jennie leads everybody in the song High Is Better Than Low . . . then she and Nellie sing The Night May Be Dark. Three weeks later the company is working to get ready for the first production in their new theater. The Harem Girls rehearse, then James and Abe sing I Believe In Takin' A Chance. Later, Jennie, alone backstage, is amazed to see Christopher enter. He's on tour with his play, but his purpose is to present Jennie with the script for his new play and offer her the leading role on Broadway. In comes James; he burns with resentment and stalks off.

Jennie and the Script
Alone, Jennie reads aloud from the script, realizing that Christopher has drawn on her Irish family and Irish stories for his play. Scene Four: with the house packed and James nowhere to be found, a huge crate is suddenly delivered backstage, and out steps the missing James with a live pony-symbolic present for Jennie. The show starts, and Jennie in harem costume performs the comedy lament Lonely Nights.

Tragedy strikes during the presentation of The Sultan's 50th Bride when, thanks to one of James's over-ambitious props, a flash fire sweeps the theater. True to form, James goes out and gets drunk - and returns and rants at Jennie to leave him. The show ends with Jennie on the train leaving for New York and the lead in Christopher's play. She reprises Before I Kiss The World Goodbye - foreshadowing the great career in the theater that lies before her.