As a boy, Harriman dreamt of being a combat pilot, spending his childhood collecting squadron patches and building models of every space fighter available. At 16 he applied to and was accepted to Air Dome. Unfortunately for him, his latent telepathic ability manifested itself the first month and he was expelled due to the rule concerning telepaths serving in the military. Despite this huge disappointment, he still loved Earthforce and held a deep respect of people who served in it. So when Psi Corps offered him the possibility of working as a liaison officer to Earthforce, he embraced it, deciding that a part of a dream is better than none at all.
In September 2258 he was attached to Earthforce Internal Affairs and accompanied Colonel Ari Ben Zayn to Babylon 5 to investigate the loyalty of the Babylon 5 staff, as a part of a program recently instituted by then Vice President Morgan Clark and following concerns that weapons used by the Mars Resistance were being supplied by an outer sector Earthforce base. However, the investigation, or rather Ben Zayn's involvement, may have had as much to do with Ben Zayn's association with Psi Cop Alfred Bester and the fact the Colonel was passed over for the position of Babylon 5's commanding officer in favour of the lower ranking Jeffrey Sinclair.
Sinclair convinced Agent Gray to scan Ben Zayn, allowing Gray to see the Colonel's true motives and prompting the Colonel to lash out. When Ben Zayn threatened Sinclair, Ivanova, and Garibaldi with a PPG, Gray projected a sensation of pain into Ben Zayn's head, distracting him long enough for Sinclair to incapacitate him. 
- It is not known what became of Gray, but assuming he survived the Telepath War, it's possible he finally got to realise his dream of serving in Earthforce.