Brandon Fayette was Walternate's lead scientist in the Alternate Universe.
Biography
Season Three
He was tasked by Walternate with inserting Fauxlivia's memory into Olivia Dunham. ("Olivia") He later conducted experiments on her to figure out how she could cross between universes without harm. ("Amber 31422")("The Abducted")
After Fauxlivia returned and she had her child, Henry, he took a blood sample from the child to activate the doomsday machine. ("Bloodline")
Walternate uses this to activate the machine. ("6:02 AM EST") Brandon is also there when Peter Bishop makes a bridge between the universes and then dissappears. ("The Day We Died")
Season Four (Alternate Timeline)
At some point Brandon is killed and replaced by an Organic Shape-Shifter who is then killed by Walternate. ("Back to Where You've Never Been")