In the 4th book/movie at the end of the Tri Wizard Tournament Harry and Cedric are sent to a graveyard. This is also the place Cedric dies (watch movie/read book to find out what happens). In the graveyard Wormtail brings Tom back. When that happens Tom and Harry duel, the Death Eaters watch. Harry is such a coward that he runs away and cries about it. When Harry is on his 5th year Tom when he is at the Ministry of Magic, takes over his body, or well tries to. Then Harry gives him a talking to about how great love is. And Tom is sent out, but strikes again in Harry's 6th year by giving Draco a mission. To kill Dumbledore and let the Death Eaters in, but Snape killed Dumbledore instead. In the Deathly Hallows Tom kills Snape because he thought the Elder Wand belonged to Snape but was wrong because I was Draco's. Tom does his best to protect Nigini (the snake) but Neville kills it. At the end of the Deathly Hallows Harry and Tom face off again but as Harry is the main charactor and Voldemort isn't and that well...Harry has love or something like that. So that is how Tom falls and rises and then falls again.