Echo is a young woman that has had her brain wiped clean.

She's a member of a unit known as "Actives" or "Dolls." These individuals have had their personalities erased. Now, Echo can be given numerous personas, all of which include new memoies and skill sets.

From there, she and her teammates are hired out for particular jobs, crimes, fantasies, and, sometimes, good deeds.

Echo Quotes

Echo: I know, I know. Actions have consequences.
Adelle: What if they didn't?

You ever try to clean an actual slate? You always see what was on it before.