Amazing Adventures #11 (April 1972) began a brief run as a Beast solo title. Hank has left the X-Men and got a job at the Brand Corporation, where he will be researching mutant genetics (although apparently without having outed himself as a mutant?). Xavier let him go, unlike the other mutants, who he has been keeping in lockdown since the events of #66 (another blow for The Hidden Years).
He successfully isolates what will later be called the "Mutant Growth Hormone", which he believes should give normals powers for a couple of hours, perhaps. His colleague Carl Maddicks develops an instant dislike for him. There's some spying shenanigans, and Beast ingests the MGH, and then well, goes blue and stuff. Well, grey at first. And then black (shown as blue). And angry. Not Jekyll and Hyde so much as just Hyde. His polysyllables fade off a bit.
In #12 (May 1972) he manages to disguise himself well enough to get back to work, instantly becoming a genius-level make-up artist after consulting a couple of books in the library. The one weakness is his inability to kiss someone. Just as well, really, as his newly-introduced love interest, Linda Donaldson, is really some kind of spy who killed Maddicks in the last issue. In #12 he gets into a misunderstanding with Iron Man, and in #13 gets set up by Mastermind (who has reformed the Brotherhood of Evil Mutants with Unus and Blob - using that name in dialogue for the first time). #14 has him fight Quasimodo, the Living Computer.
Following this Beast recovers at Patsy Baxter (neé Walker)'s place, where she discovers his secret identity as Hank McCoy. We find out here that this succession of enemies - including Mastermind's Brotherhood, has been arranged by the Secret Empire, who are Linda's paymasters. Warren pops up for an assist against Griffin, and then him and Hank talk. This is the first time any of the X-Men have seen the new Beast. Hank is left alone, and then goes to the library where he runs into Vera... (who, like Zelda, hasn't been seen since X-Men #47).
The whole Secret Empire plot is forgotten, as Vera and Hank go north, run into the Marvel bullpen in Rutland County (in a strange crossover with Justice League of America), and Beast fights and defeats the Juggernaut in #16 (January 1973). It feels more like a date than the first part of the story concluded in Incredible Hulk #161 (March 1973), where she brings Hank to her lover, Calvin Rankin/Mimic, who is dying and may take the world with him. She apparently still doesn't know Hank is an X-Man, despite knowing all about Calvin. They save the world, but not Calvin... (which of course is temporary, he pops up in Legacy in 2012, although I don't know quite how temporary).
Although the physical transformation he undergoes here is very important to his character in the future, it's a bit of a letdown to finally read this. It's not really great material for Beast, as he gets victimised and led from set piece to set piece. And it isn't caused by some kind of heroic sacrifice, the spirit of curiosity, or even (as in the 2011 film X-Men: First Class) an attempt to cure himself. It's just idiotic, as he himself recognises.