The Master strikes back with his own agenda in the next episode of "The Strain." Episode 10, titled "The Assassin," will show Dutch and Eph battle the evil servant of The Master. The next series episode will also show Setrakian's continued search for the Occido Lumen, in his quest to kill The Master once and for all.

According to TV Guide, episode 10 of the FX vampire series will show the unusual team up of Eph, played by Corey Stoll, and Dutch, played by Ruta Gedmintas, to kill The Master's evil ally. In the previous episodes of the series, Dutch was patrolling the streets of New York, killing off vampires with Vasily Fet, played by Kevin Durand.

"The Assassin" will also bring Setrakian, played by David Bradley, closer to the end of his search of the Occido Lumen, the book that's believed to contain the answers on how to kill The Master. His hunt for the owner of the book could culminate in episode 11, titled "Dead End," since according to a separate TV Guide entry, Setrakian will meet a familiar face during his search.

IGN says the Occido Lumen seems to be the driving force of the story in season 2 of "The Strain." However, the book has not been revealed or discussed in detail in the previous series episodes. The owner of the book has only been teased in episode 8, titled "The Intruders."

In this episode, Fet and Setrakian learns the Occido Lumen is with the cardinal so they pay him a visit to buy the book, according to TV Guide. However, they learned that the cardinal has placed a betting game on the book between Setrakian and Eldritch Palmer, played by Jonathan Hyde.

After the cardinal refused to sell the book, Fet and Setrakian agree to come by in the evening to steal it. However, by night-time they found the cardinal lying on the floor, infected with the deadly vampire disease. The Master's assistant, Eichorst, played by Richard Sammel, has also paid the cardinal a visit and infected him after he refused to reveal the location of the Occido Lumen.

However, the cardinal tells Setrakian that the book is with Rudyard Fonescu, the only survivor in the vampire massacre in the Austraian nunnery in 1966. Setrakian then kills the cardinal so The Master won't be able to read his mind and know the whereabouts of the book himself.

A flashback scene in episode 4 of "The Strain," titled "The Silver Age," shows a young Setrakian and a wheelchair-bound Palmer visiting the nunnery after Setrakian learns the book is there. However, they meet a boy, Rudyard Fonescu, who tells them that the Mother Superior has burned the book, believing it was evil.