Spanners
The average human being lives from 0-80 sequentially. Spanners don't.
These rare beings have different lifespans than the rest of us. Some live their lives in reverse, some live only six months, and some are immortal. There are hundreds of classes of spanners that live hundreds of different ways, and each class has a unique lifespan that gives them unique powers.
A few spanners find a way to live in normal human society, but most live in the shadows. There are some spanners that are extremely dangerous, and with the help of a mayfly-class spanner, an 8,000-year-old detective named Adam Parr is doing everything he can to keep them under control.

The Fountain of Youth
When one of Adam's old adversaries uncovers the most powerful and deadly spanner in history, it's up to Adam and Mayfly to take her back before she unleashes her full power and ends the world as we know it.