Darkness Visible continues the adventures of Dr. Mercy Teller as she fights through the aftermath of the cataclysmic events that took place in "Forever Fallen." From an archaeological dig site on the coast of the Black Sea to the city of Timisoara where she almost died years earlier, Mercy finds that she has not reached the end of her quest, but in learning more about her own history and her growing abilities, she steps into ever more dangerous events. Along the way, Mercy discovers a widening series of impacts that threaten to engulf her, the ones she loves and the world around her.