Ricardo hated Reed Richards for being lauded as his mental superior, and planned on infiltrating the Fantastic Four in order to destroy him. He met Thing on his own, befriending him and inviting to his apartment for a cup of coffee.
While there, Ricardo slipped a sleeping pill into Ben's coffee, and while he was asleep, used his Duplication Apparatus to take Ben's form away from him and put it on himself. Then, having a body exactly like the Thing, he went back to the Fantastic Four to take Ben's place.
Ben showed up in his normal human form, but was unable to convince Reed and Sue that he was who he said he was, and left upset.
Reed continued his dangerous experiment, creating a portal to orbit above Earth. He planned on venturing through the portal, tethered by a line that "Ben" (who was really Ricardo) would hold, to be able to pull him back through the portal. The tether line snapped, and unable to do much else, Ricardo jumped through to help Reed. While falling into orbit and being burned up in the atmosphere, he learned that Reed was a great guy, and took this chance to do a good thing for the first time in his life. He threw Reed back through the Portal, and died when he was burned up in re-entry .