Sirius Black
Background
Sirius Black is a convicted murderer incarcerated in Azkaban Prison. He is an animagus and can take the form of a dog. Sirius was sent to prison for the murder of Peter Pettigrew and is believed to have betrayed Lily Potter and James Potter to Voldemort. His cousins are Bellatrix Lestrange and Narcissa Malfoy.
During the events of Harry Potter and the Prisoner of Azkaban (2004) played by Gary Oldman
Harry Potter sits down on the edge of a sidewalk and sees a black dog. Later the black dog appears and charges at Ron Weasley and drags him under the roots of the Whomping Willow. Harry and Hermione Granger follow Ron's screams and find Ron in a room with Sirius. Harry threatens to kill Sirius, but is disarmed when Professor Lupin bursts into the room. Lupin and Sirius hug and Hermione thinks Lupin has betrayed Harry. Hermione tells Lupin she knows he is a werewolf. Lupin tells Harry it wasn't Sirius that betrayed Lily and James, but Peter. Professor Snape runs into the room and disarms Sirius. Harry uses his wand to knock Snape unconscious. Scabbers tries to run away and is transformed back into Peter and is caught. As Sirius and Lupin are about to kill Peter, Harry stops them and says Peter needs to be taken to the castle and given to the authorities. They all exit the cavern under the Whomping Willow and Sirius tells Harry he will be happy to be a free man again. Sirius offers to have Harry live with him and Hermione yells out when the full moon starts to peak over the horizon. Lupin starts to change into a werewolf and Peter manages to escape. Sirius yells at Harry, Ron and Hermione to run. Snape walks out of the tunnel and is swiped at by Lupin who has completely transformed. Sirius and Lupin fight and Harry throws a rock at Lupin distracting him. Something from far away howls and Lupin runs towards the howl. Sirius crawls away and Harry finds him wounded near a lake. The air starts to get colder and a group of Dementors circle above. They start to attack Sirius and Harry casts the Patronus Charm and is then attacked by the Dementors. As Sirius' soul is about to be taken, a glowing stag appears and forces the Dementors to retreat. The stag disappears and Harry collapses next to Sirius. Sirius is captured and brought to the Dark Tower. Harry and Hermione ride Buckbeak to the Dark Tower and free Sirius from prison. Before leaving, Sirius tells Harry he looks like James, but with Lily's eyes and tells Hermione she is the smartest witch of her age. He then flies away on Buckbeak.
During the events of Harry Potter and the Goblet of Fire (2005) played by Gary Oldman
Harry writes a letter to Sirius telling him of the dream he had and gives it to Hedwig to deliver. Later, Harry gets a letter from Sirius telling him to meet him on Saturday. Harry goes to the Gryffindor common room and Sirius appears in the fireplace. Sirius asks Harry more details about his dream and tells him Hogwarts isn't safe.
During the events of Harry Potter and the Order of the Phoenix (2007) played by Gary Oldman and James Walters
Harry, Nymphadora Tonks, Alastor "Mad-Eye" Moody, Kingsley Shacklebolt, Elphias Doge, and Emmeline Vance go to Grimmauld Place where Sirius is having a meeting with Mr Weasley, Lupin, Professor McGonagall, and Mrs Weasley. The meeting ends and Harry says hello to everyone and Sirius gives him a hug. Kingsley hands Harry a newspaper where Cornelius Fudge is accusing him and Albus Dumbledore of lying about Voldemort. Sirius tells Harry that Voldemort has been trying to recruit followers and that Voldemort is trying to get something he didn't have last time.
Harry goes to leave for Hogwarts, but before he does, Sirius gives him a photo of the original Order of the Phoenix, which included Neville Longbottom's parents. Sirius appears in the Gryffindor common room fireplace and tells Harry, Ron and Hermione that Fudge thinks Dumbledore is trying to form a wizard army to take on the Ministry of Magic. On Christmas, Harry, Sirius and Hermione join the Weasley family at Grimmauld Place for Christmas dinner and gifts and Mr Weasley is shown to be recovering from his attack. Harry walks into a tapestry room and Kreacher critiques Harry and his friendships. Sirius sends Kreacher away and explains his family tree to Harry. Harry tells Sirius that he is worried that he is becoming like Voldemort.
Snape continues to train Harry in Occlumency, and Harry manages to get into Snape's memories and sees a memory of Snape's where he is picked on by James, Sirius, Peter Pettigrew and Remus. The Order of the Phoenix arrive at the Department of Mysteriesand another battle starts. The prophecy is destroyed when Lucius drops it. Bellatrix casts the Avada Kedavra spell against Sirius, hurtling him towards the Veil, which absorbs him.
