Hunter x Hunter - episode 35 - 21 Jul, 2000

Killua's mother Kikyo and brother Kalluto knock Canary out. They tell Gon that Killua doesn't have time to see them and they should leave. When Canary wakes up, she and Gon's group head to the house of security guards. Meanwhile, Killua has a talk with his father Silva, who makes Killua promise to never betray his friends. He then lets Killua leave to find Gon. Later, Silva tells Kikyo that Killua will be back because he's his father's son. (Source: Wikipedia) Zoldyck Family arc: (4/5)