This is a mystical and confusing flick, in the "arty" science fiction genre. It jumps around between three different eras: the 1500s, the (roughly) present-day, and the far-flung future where they can make cool interstellar spaceships that look like soap bubbles.
Hugh Jackman plays (in the modern day) medical researcher Tom, trying to save Rachel Weisz as his desperately ill wife Izzi, using that a compound extracted from a Central American tree. Their 16th-century counterparts are conquistador Tomas and Queen Isabella of Spain, threatened by the Inquisition, in need of the fabled Tree of Life, coincidentally located in Central America. And in the future scenes, Jackman's character is an astronaut, transporting a dying tree to a dying star within a gaseous nebula.
But it's all pretty interesting, and it's fun to notice the connections made between the three eras, and to (at least attempt to) figure out what's going on. I would have thought the critics would have been kinder to the movie, but it scores a mere 50% over at the Rotten Tomatoes site. Apparently, it's too arty for some.