Although marketed as a drug, Returné is actually a nanotech-laced serum with the rather unusual effect of raising the dead – although not forever. A single injection lasts for about 24 hours before needing to be replenished (although actual death doesn’t result for another five or six days).
Because users of Returné are actually dead, they are immune to aging and illness. In fact, they are mnore or less immune to any thing that might cause death other than immolation, dismemberment or dissolution (that is, acid bath suicide).
The drug was produced by shadowy Big Pharma company Pharmadene, which goes a way towards explaining why this nanotech miracle isn’t permanent when it so easily could be – where’s the money in that? The drug has not yet been cleared by the FDA for public use, although it rapidly leaked out through an underground of criminal funeral homes, from which it was sold at exhorbitant prices. As a result, a shadowy war of corporate espionage and covert law enforcement broke out, whose outcome is still unclear at this time.