Malcolm was the member of an idle rich mutant family in the years after the fall of the Sentinel mutant camps. He chose to join the XSE in order to prove himself above and beyond his family's wealth. Assigned to Bishop's unit, his commander was initially reluctant to "babysit" a rich donor's pup, until Malcolm showed off the fire in his belly.
Along with Bishop's other pick, Randall, the three became Omega Squad. Malcolm and Randall didn't always work well together. The strict, by-the-book Malcolm clashed with the free-spirited maverick Randall until the massacre of Harmony Base. Malcolm's brother Donalbain was part of the commune, and his death brought the squadmates closer together. The three became good friends and Bishop turned down promotions to continue to work with them.
The trio followed Trevor Fitzroy and a number of other criminals through a portal, where they encountered the X-Men. Bishop, Malcolm, and Randall later found the remaining criminals in a bar. In the ensuing firefight Malcolm and Randall were killed, sacrificing themselves to protect Bishop. Malcolm's last words were "Sir, you're too important..."