Talus sent Initiate Jonathan to the Hub with an assignment. Although he did not expect trouble, Decker decided that the lone man would make a perfect source of information about the Brotherhood of Steel. They jumped and imprisoned him, torturing him for information and feeding him a variety of mind-altering drugs. Talus would be grateful for his return.
The Initiate is located in the Old Town of the Hub, in the building just by the exit grid. The quest can be completed at any time, even without talking to Talus. However, the Initiate is guarded by four rough guards packing plenty of firepower (a combat shotgun, two 10mm SMGs, and the fists of a talented melee fighter). They can be attacked by opening the door or shooting at them through the windows. A party and some good armor are recommended for surviving the ordeal.
Afterwards, the player has to lockpick the door in the back and release Jonathan by talking to him. Talus will give the reward after gaining access to Lost Hills.