In 1944 Hellboy was conjured in a ceremony meant to give Hitler the ultimate occult weapon. Fortunately, Professor Trevor Bruttenholm was there to witness and to guide Hellboy to become the world’s greatest paranormal detective. But Bruttenholm wasn’t the only witness to Hellboy’s arrival. This collection reveals the aliens who monitored Hellboy’s arrival, and why the assassin they sent to Earth stayed his hand. Collects The How and Why He Stayed #1–#5 and the The How and Why He Stayed short story from Hellboy Winter Special 2017.