Sadler is a mad scientist who has apparently usurped control of the criminal organisation known as Shadaloo and is using their resources to acquire different martial artists from all over the world in one of his laboratories. His intention is to analyse and absorb all of their chi (spiritual energy, though he just refers to it as data) to increase his own power, and intends to use all of this combined power to take over the world. In order to lure in the Shotokan expert Ryu, Sadler employs a boy by the name of Shun to pose as Ryu's long-lost younger brother. Shun wins Ryu's affections and the two later participate in a Street Fighter Tournament, unaware that Sadler is hosting the competition.
During the tournament, Sadler witnesses Ryu tapping into the power of the Satsui no Hado (aka the Dark Hadou) and decides that he wants to add that power to his own. He sends his android Rosanov to attack Ryu and Shun in order to gauge their potential and Rosanov is destroyed when Ryu fires off a Dark Hadoken. Shun is injured during the struggle and Sadler's agents abduct the boy, taking him to Sadler's desert stronghold.
A day later, Ryu, Ken Masters and Chun-Li board a plane bound for Sadler's lab where the professor is hosting another Street Fighter Tournament, intent on collecting the chi of the participants and gaining all of their skills and powers for himself. He sends another Rosanov cyborg to attack Ryu and his friends, but this one has Shun inside its body. Rosanov/Shun goads Ryu into using the Satsui no Hado as that is the only ability that will defeat him. Ryu gives in to the darkness and destroys Rosanov, setting Shun free but injuring him at the same time.As Sadler's body absorbs the energy of Ryu's attacks, his body spasms in fits of ecstacy. After absorbing the Dark Hadou, he transforms into a muscle-bound, grey-skinned superhuman with beady red eyes. Sadler relishes the new power he wields and proceeds to savagely beat Ryu, who does little to fight back. Ryu manages to snap out of his dark haze brought on by the Dark Hadou and he retaliates by firing a Shinku Hadoken at Sadler. The blast of pure chi energy strikes Sadler and badly damages his body, destroying both his arms. Before he can question how Ryu could be so powerful, Sadler's body crumbles to ash.