In 1966 during the Nursery Standoff Boomer caused the death of Eagle, Zander’s military specialist. Zander’s experimentation revived Eagle’s body to an obedient zombie-like state. It is unclear whether the thing controlling Eagle is his own brain or the Jynx Elixir that now runs through his veins. 

Both agents and villains sides are defectors from the Soviet Union, but the teenagers were trained to infiltrate America so have developed and maintained American attitudes and personalities. None of them consider themselves as  “American” but believe they are international citizens of the world.

The top secret Jynx Crystal technology that gives the 5 main agents their immortality is not fully understood.