The title or saying above can cover two interpretations -
1 It means an avenging sword, sharpened both sides, to cut two ways.
2 It can also represent 'payback', ot in another term 'revenge'.
In this book the latter meaning comes into play.
Rhia Bryant finds herself caught in a web of deceit and lies, the pathway, if not discovered, that could lead to destruction. Her beloved father appears to have gone missing, and it all relates back to his younger self, and his past.
It is often questioned into whether the past can collide with the present - this is your chance to find out.The Double Edged Sword