DC Special changes format with issue 22 (June/July 1976), becoming a mix of new and reprinted material. The Three Musketeers begins as the lead feature, with Robin Hood reprints as back up. In this case, one from Brave and the Bold, and one from Robin Hood Tales.
The Three Musketeers had briefly appeared in More Fun Comics in the late 30s, in an adaptation of the Alexandre Dumas novel, and then had made occasional guest appearances in other series. This new run was created because of the popularity of the Richard Donner movie. Denny O'Neil and George Moliterni set this story at some point during that film, as D'Artangan is not yet a full musketeer, he has not received his commission, although he is already friends with Athos, Porthos and Aramis.
The Musketeers are on a mission to deliver a letter to the Spanish ambassador, negotiations in advance of a peace treaty. Others want to steal the letter and learn its contents for their own reasons, but really it is just something for people to fight over.
The Musketeers come to the aid of a young woman, Charlotte DuBois, but also find themselves facing a big hair monster.
The woman and the monster never appear at the same time, although one often appears just after the other vanishes. It doesn't take too much effort to guess that they are the same person.
It makes for a relatively odd start to the series, as Charlotte turns out to be a witch, with an amulet that allows her to change form. There is no magic of any sort in the Dumas novel, or the Donner film.