By the 22nd century, the "Howard families" have a life expectancy exceeding 150 years and keep their existence secret with the "Masquerade" in which the members fake their deaths and obtain new identities.

Administrator Slayton Ford, leader of Earth, believes that the Families are telling the truth, but cannot prevent efforts to force Howard members to reveal their alleged rejuvenation treatments.

Using an inertialess drive invented by Howard member Andrew Jackson "Slipstick" Libby, the Families leave the Solar System with the deposed Ford.

A majority of the Families returns to Earth to demand their freedom; Libby, with the help of the group mind, builds a new faster-than-light drive to take them home in months instead of years.

Alva Rogers, in A Requiem for Astounding, wrote that Methuselah's Children was "Full of adventure, conflict, romance, and enough casually tossed-off ideas to serve as the basis for a half-dozen other stories.

For one, its main theme, the problem of escaping death, is one that keeps cropping up in Heinlein stories, and for another, an amazing number of brilliant ideas are tossed out along the way.