The advertising campaign (to the extent that there is one) compares Tristan & Isolde with Romeo & Juliet. The better association, as indicated above, is Arthur (Lord Marke), Lancelot (Tristan), and Guinevere (Isolde).
In fact, just making that comparison gives away a lot of the plot.
O'Hara's increasingly over-the-top turn is almost laughable, but Myles ("Underworld") does have some presence.
Fate has different plans, however, as Isolde's father offers her up as a prize to the British lord who can unite the various warring territories.He has been trying to get this movie made for about 25 years.And, although he ultimately didn't direct it (that task went to Kevin Reynolds, best known for his two Kevin Costner vehicles, Robin Hood: Prince of Thieves and Waterworld), he had to stand by and watch the distributors let it gather dust sitting on their shelves for a year while they tried to figure out how to handle it.In order to better ground the tale, the filmmakers have removed references to sorcery (much as Wolfgang Petersen stripped the gods out of Troy).
Tristan & Isolde begins shortly after the fall of the Roman Empire, probably around the 7th century.James Franco's performances to date have been equal parts swagger and petulance, which is why he's been so convincing as James Dean in a made-for-television movie, as a malcontent high school student in TV's "Freaks and Geeks" and as a spoiled industrialist's son in the "Spider-Man" movies.