If you're wondering what Citizen Kane might have looked like had it been produced by MGM, we submit for your approval Keeper of the Flame. War correspondent Spencer Tracy is assigned to write the life story of a recently deceased super-patriot. One would suppose that the much-beloved decedent's life would be an open book, yet his widow Katharine Hepburn refuses to release any details concerning her late husband. Tracy gains Hepburn's confidence, and she agrees to help him with his article. Several curious incidents lead Tracy to believe that Hepburn was in some way responsible for her husband's death. While this is not entirely the case, Tracy stumbles upon a truth that has been carefully hidden from the public by the dead man's "damage control" people. Adapted by Donald Ogden Stewart from a novel by I. A. R. Wylie, Keeper of the Flame is perhaps the most dour of the Tracy/Hepburn vehicles; those expecting the usual battle-of-the-sexes repartee between the two stars would be better off with Adam's Rib or Pat and Mike.
~ Hal Erickson, All Movie Guide