In The Granite Key, an antique dealer is murdered for a mysterious cipher stone that reveals the location of a collection of ancient artifacts. The victim's sister Cassie is stunned when she learns about her sibling's double life as an Arkana agent. She's even more stunned to discover the role she's about to play in helping the Arkana recover the trove. Along with two field agents, she travels to Crete to hunt for clues, unaware that ruthless Nephilim operatives are only steps behind.

In The Mountain Mother Cipher, the race is on between Arkana agents and Nephilim operatives as they rush off to Turkey in search of clues leading to legendary artifacts. Among ancient megaliths on the top of Mount Ida, the foes square off in a literal cliffhanger of a confrontation. At the worst possible moment, the Arkana crew discovers that the Nephilim aren't their only competitors for lost treasure. Unforeseen obstacles and unknown enemies thwart their efforts to complete their mission and escape unharmed.

Agents of the Arkana and the Nephilim leave no stone unturned on the island of Malta in their search for lost artifacts. The Arkana team frantically scavenges for clues among the ruined temples of the archipelago before their foes arrive to comb the same terrain. Matters come to a head in an isolated mountaintop cave when the relic hunters learn that their prize can only be discovered if they "keep true to the dragon's wing". With Nephilim operatives blocking their escape route, will they live long enough to solve the riddle?

College freshman Cassie Forsythe wakes from a disturbing nightmare after seeing her sister being murdered by a man in a cowboy hat who demands something called "the key". Her dream morphs into frightening reality when her sister is found dead, exactly as her vision foretold. Cassie's life takes an even more bizarre turn once she learns that her dead sister, an antique dealer, has discovered the location of a cache of priceless Minoan artifacts.

Into the Jaws of the Lion finds the Arkana agents on a new adventure in India where they search for a jewel-encrusted figurine that holds a clue to an even more priceless artifact. Beating the Nephilim to the prize is the least of their worries. Back in the States, the cult's leader has evolved a plan to release a deadly plague on an unsuspecting world just as his henchman zeroes in on the whereabouts of his child bride. Every effort to throw the hunter off the girl's trail only draws him nearer to his prey.

In Secrets of the Serpent's Heart, two Arkana agents search the length and breadth of China for an obscure relic that will name the hiding place of their most sought-after prize. At the same time, a third agent tackles the dangerous mission of discovering the Nephilim's end game. In the remote reaches of Yunnan province, the agents encounter an enigmatic stranger who holds the power to stop their quest dead in its tracks.

College freshman Cassie Forsythe wakes from a disturbing nightmare after seeing her sister being murdered by a man in a cowboy hat who demands something called "the key". Her dream morphs into frightening reality when her sister is found dead, exactly as her vision foretold. In the series finale, the Nephilim and the Arkana scour the farthest reaches of the planet for the hiding place of the legendary relic known as the Sage Stone. At the same time, mortal danger threatens friends and foes alike as the cult's leader pushes humanity to the brink of extinction.