Lupin was in the Marauders when he attended Hogwarts School of Witchcraft and Wizardry. He joined the Order of the Phoenix in the First Wizarding War. For a year, he was Defence Against the Dark Arts Professor at Hogwarts. He joined the Order again in the Second Wizarding War, and was killed at the Battle of Hogwarts.
At a very young age, Lupin was bitten by a werewolf. His parents tried everything they could to help, but lycanthropy doesn't have a cure and the Wolfsbane Potion was yet to be invented. Because he had to turn into a werewolf, a very dangerous beast, he thought he would be unable to attend Hogwarts School.
Before he would have been due to start Hogwarts, Professor Dumbledore became Headteacher of Hogwarts and he was sympathetic towards Lupin. He agreed he could attend Hogwarts School if he agreed to certain rules for safety. Lupin accepted and the school was adapted before he started.
Dumbledore built a boarded-up house (the Shrieking Shack) where Lupin would have to go and get chained up when he turned. He built a secret passageway for Lupin to get to the house. The passageway was accessed in school grounds by tapping a knot in a Whomping Willow, which he planted to cover and guard the entrance.
In September 1971, he began attending Hogwarts School and was Sorted into Gryffindor House. He befriended James Potter, Sirius Black and Peter Pettigrew. They were inseparable, but he didn't tell anyone he was a werewolf. He invented stories when he kept disappearing, but they worked it out in their second-year.
Rather than shun Lupin for being a werewolf, they were supportive. They began training to turn into Animagi so they could keep Lupin company in the Shrieking Shack. Because he was chained up in the Shack, he couldn't hunt and eat so he would scratch himself, broke furniture and howled. The noises caused villagers to think it was haunted, and even ghosts thought a bad crowd lived in it.
Lupin was a good student, but he and his friends were pranksters. He and Peter got into less trouble, but ended up in detention a few times too. Lupin got to be a Prefect, but he couldn't discipline his own friends even though they broke school rules. Their pranking could go too far, and turned into bullying. They were very cruel to a Slytherin student, Severus Snape who they kept taunting and attacking. Lupin didn't personally do anything to Snape, but he stood by and let it happen and would later wish he had tried to stop it.
Having trained for three years, his friends were able to turn into Animagus. James was a stag and Sirius was a dog, and were both large enough to control a werewolf if needed. Peter was a rat and was useful for tapping a knot in the Whomping Willow to subdue it. When he was a werewolf, their company helped lessen the pain and his mind was less of a beast. They began to gain confidence and were soon letting Lupin loose and wandering the school grounds. He felt guilty because he was betraying Dumbledore's rules, but he would call these days the best days of his life.
But one day, he was spotted by Snape being taken to the Whomping Willow by Poppy Pomfrey and he was curious to know why. He annoyed Sirius by asking, and he ended up telling Snape how to tap a knot in the tree to get into a secret passageway to find out why. James had to pull Snape back before he got too close, because he would have been killed by Lupin. He saw the werewolf at the end of the passageway, and was forbidden by Dumbledore to tell anyone. The incident was a cause of Snape's bitter anger towards their group.
First Wizarding War
Lupin joined the Order of the Phoenix when he graduated Hogwarts. He struggled to find work because he was a werewolf, so he was financially supported by James because he could afford to.
It was later deduced that a spy was in the Order passing their secrets to Voldemort. James and Lily Potter had to go into hiding due to a prophecy that their child, Harry Potter would have a power to defeat Voldemort. Sirius suspected Lupin was a spy. Lupin knew James and Lily used a Fidelius Charm and intended their Secret Keeper to be Sirius. However, because they thought he could be a spy, Lupin wasn't included in their plan when they switched their Secret Keeper to Peter.
Unfortunately, Peter happened to be the spy and James and Lily died. Lupin thought Sirius was their betrayer, and that he had later killed Peter too. Sirius was sent to Azkaban, leaving Lupin lonelier than ever.
Prisoner of Azkaban
In September 1993, Lupin chose to travel by train to Hogwarts. He was sleeping in a train compartment when coincidentally, Harry Potter, Ron Weasley and Hermione Granger chose to travel in it too. Ron wondered who he was, and Hermione saw he had a name engraved on a trunk saying "Professor R. J. Lupin". She deduced he was going to be teaching Defence Against the Dark Arts.
Lupin didn't wake up, even when Hermione tried to offer food. But they used Lupin to deter Draco's gang, because a Professor would have heard their taunting. The train later stopped later when Dementors wanted to board and search for Sirius Black. A Dementor searched their compartment, but began draining Harry instead of searching for Black. Harry fainted and Lupin had to intervene using a Patronus Charm. He gave Harry a piece of chocolate when he woke up.
Lupin soon went to speak to their train driver, and sent an owl ahead to Hogwarts to tell the school what had happened. He popped back later to check on Harry, who he had to encourage again to eat the chocolate he had given out earlier. Even though Harry hadn't been introduced by name to Lupin, he found it very curious that Lupin had known it anyway. When they arrived at Hogwarts, Lupin overheard Draco taunting Harry and Ron again and asked if everything was okay.
Lupin had a young face when he was in his mid-30s and light-brown hair which had flecks of grey. But because of the suffering he endured being a werewolf, he tended to look tired and pallor and his face had lines in it. He usually wore shabby clothing.
Notes and sources
- Harry Potter and the Prisoner of Azkaban, Chapter 7
- Harry Potter and the Prisoner of Azkaban, Chapter 17
- Harry Potter and the Prisoner of Azkaban, Chapter 18
- Harry Potter and the Prisoner of Azkaban, Chapter 19
- Harry Potter and the Prisoner of Azkaban, Chapter 5
- Harry Potter and the Prisoner of Azkaban, Chapter 10