A few months after the end of his run in Showcase, and only a couple of months after teaming up with the Flash in Brave and the Bold, the Spectre moves into his own series with the Nov/Dec 67 issue. This was the first ongoing DC series actively set on Earth-2.
Gardner Fox and Murphy Anderson handle the story, which is ok, but not quite up to par with his Showcase adventures. A noted ambassador gets shot by an assassin, and the experimental surgery done on him winds up bringing forth the spirit of Captain Blood, a pirate ancestor, who takes control of the ambassador's body.
Jim Corrigan is put onto the case, and his Spectre self finds that he is unable to make direct contact with Captain Blood, due to the "megacyclic" energy in the spirit.
The story takes on a time travel element, with the Spectre going back to other ancestors/descendants of the ambassador/Captain Blood, in medieval and ancient Roman times, trying to defeat the evil spirit in those periods, though it keeps escaping.
The Spectre finally resorts to charging up his own body with megacyclic energy so that he can fight Captain Blood directly. The art is good, but the villain is kind of lame, and doesn't seem enough of a threat for the Spectre.