The Three Musketeers series comes to an end in DC Special 25 (Dec/Jan 76/77), an issue that has three reprints in it as well, all from the pages of Brave and Bold. Two feature Robin Hood, while the third is of the Viking Prince.
Boltinoff and Elias are joined by John Calnan for this tale, which opens with the execution of Corbeau, arrested in the first Three Musketeers tale for trying to overthrow the King of France.
For his part in bringing in Corbeau, D'Artagnan is made a duke, and given Corbeau's castle, the Raven's Roost. Corbeau had made a cryptic reference to a raven as his dying words. D'Artagnan heads out to take possession of his new castle, but winds up challenged by a masked man, cleverly named the Mask, who has been raiding in the area.
D'Artagnan also gets attacked by a woman the night he arrives, but stops fighting when he sees Corbeau's ghost. He is not sure that this really happened, and goes to sleep beneath paintings of ravens. He awakes to another attack by her, which is stopped by Athos, Porthos and Aramis, who have come to hang with their old friend.
The woman turns out to be the daughter of Corbeau, who believes her father was innocent and D'Artagnan is evil for having him killed. While D'Artagnan spends his time trying to win over the girl, who he has fallen for, the other musketeers go around collecting the taxes he needs to pay the king. They get them, but then all the money gets stolen by the Mask. D'Artagnan notes that one of the ravens in the paintings has been repainted, and makes some really impressive guesses as to what is going on.
D'Artagnan arranges a big marriage between himself and Corbeau's daughter, which the Mask tries to stop, as D'Artagnan had intended. He removes the man's mask, revealing him to be Corbeau. It was his twin brother who had been executed in his place. The daughter realizes her father was not innocent, and turns on him. Corbeau tries to escape, but winds up losing his head anyway.
Now the daughter is more than happy to marry D'Artagnan, but he decides he doesn't really want her, or the castle, and resigns his position as duke to continue life as a musketeer. Since the series came to an end, it probably wasn't the best choice.