William Afton and Henry Emily are characters from the Five Nights At Freddy's videogames and novels.
Once good friends and business partners, their relationship was slowly torn asunder when William murdered Henry's toddler-aged daughter Charlie. This initial burst of bloodlust kicked off William's killing spree, and he went on to murder more children. The vengeful spirits of the children possessed the animatronics at William and Henry's pizzeria, their only goal to murder adults--especially ones that resemble William.
Henry's life after Charlie's murder takes two very different routes depending on the canon--however, both end in tragedy. In the games, he spends 30 years tracking William down, finally cornering him in FNAF6: Pizzeria Simulator. He sets the building on fire, killing both William and himself, and doing what he believes to be freeing the spirits of Charlie and Elizabeth trapped inside animatronics.
In the novels, Henry is driven insane by Charlie's murder. Despite his miraculous effort at recreating his daughter's soul and placing it into a humanlike robot (indistinguishable as human to everybody except William), Henry's grief and rage are too much for him to bear. As his psychosis hits its peak, he commits suicide. It is implied that he had suspicions about William's involvement in Charlie's murder but was never quite sure, possibly due to their close past together.
"Don't keep the devil waiting, old friend." - Henry's last words to William before killing them both (FNAF6).