In the late 2260s, Jonas was appointed to be James' assistant by the Overseer, who hoped he would be a voice of reason. Jonas and James forged a friendship very quickly and together they worked at examining and treating patients, as well as conducting routine experiments testing the health of the Vault. For an unknown length of time, James deliberately kept his assistant in the dark about covert experiments aimed at reviving Project Purity. Eventually, Jonas grew suspicious of the physician's activities and by mid-2274, Jonas was willingly aiding James with experiments related to Project Purity.
When James escaped from Vault 101, Jonas was killed by Officer Mack for trying to help James open the Vault.
Growing Up Fast: Jonas is first encountered during the Lone Wanderer's 10th birthday when your dad takes you down to the generator room to give you your present (a BB gun). Jonas takes a picture of you and your dad.
Escape!: The Note from Dad holodisk can be looted from Jonas's body, containing a message pertaining to James' escape.
After the Lone Wanderer receives a BB gun for their 10th birthday and kills a radroach, Jonas is able to be punched or shot until he is unconscious. However, he will still take the photo of the Lone Wanderer and their father while he is unconscious.