Meet Mercy Lake. She likes to fix things: broken toys, old appliances. People.

She watches them in the dead of night, identifies what their lives are lacking and gives it to them . . . quietly. So quietly, they don't even know she exists.

Then Mercy meets Louis. He believes some of these people deserve punishment, not help. Joining up with him to dispense a little harmless justice feels good - at first. But when people start getting hurt, Mercy must decide if the ends can ever justify their increasingly violent means.

And soon, their interventions draw the attention of the very person Mercy embraced her nocturnal existence to evade. Someone who will go to extreme lengths to make her pay for knowing their secret . . .