FORT WORTH — The only thing more inevitable than death and taxes is familial discord.That is one of the insights proffered in Death Tax, a play about money, relatives and mendacity that received its regional premiere at Amphibian Stage Productions on Thursday night.This tidy, one-act drama, which sprinkles in just a few comic moments, tells the story of an elderly woman believed to be dying in a nursing home, her fortune, her daughter and the medical staff caring for her. It is set in the recent past and comprises five scenes. In the first, we learn that the woman, Maxine (Georgia Clinton), is convinced that her nameless daughter (Laurel Whitsett) is paying her nurse Tina (Stormi Demerson) to slyly kill her before the end of the year when a change in the tax laws will cut the daughter out of a large share of a substantial inheritance. Tina’s reaction when Maxine bluntly accuses her of being a murderer sets off a series of events that are as explosive as they are unexpected. So not another word dare be said about Lucas Hnath’s plot, except that it is full of twists and turns that spiral its characters deeper into an abyss they collectively create. This production, deftly directed by Rene Moreno, is overflowing with outstanding performances. Clinton, who wowed audiences as title columnist in Red Hot Patriot: The Kick Ass Wit of Molly Ivins at Stage West last year, is razor-sharp and steel-strong as the ailing but well-heeled matriarch. Demerson, who employs a great Haitian accent, carries the show during most of the first four scenes. John Forkner, doubling up as Tina’s boss and Maxine’s grandson, manages to make his characters simultaneously sympathetic and pathetic (no easy task). And Whitsett is quite powerful in the brief moment the script gives her. Their machinations are played out across Bob Lavallee’s simple but chicly sleek set that ideally matches the lean, mean direction and writing.If there is any problem with play, it may be that Hnath tends to write extraordinarily long speeches for his characters, who bare their souls at the drop of a hat. This gets a lot done in a short time, but it also creates odd rhythms. As for the production itself, a sound design that is supposed to reflect a hospital ambiance should be turned up or off. At the mumbling level it was set at Thursday, it sounded more like cell phones were mutedly chattering. This show is ultimately about our health care system and who is going to pay for what in the future. But the world that Hnath, Moreno and this superb cast creates is so immediately compelling that those larger issues are left for later enjoyment. Because this is a show is likely to stick with you. Like death and taxes.