How was Voldemort able to touch Harry Potter in the Goblet of Fire film?

Please, no spoilers. I've just concluded the film Harry Potter and the Goblet of Fire. I don't know what occurs in any of the subsequent films. Why is it that Voldermort was suddenly able to touch Harry in the graveyard scene of this film? Why didn't the love-based protection against Voldermort Harry's mother casted work?