Secret Passage - Jews of 15th/16th century Spain and Venice

I just saw the award-winning film Secret Pasage at the Jewish Film
Festival, and a friend who was there with me said that the closing
credits referred to a novel from which the story was developed. I
didn't see those credits though and haven't been able to find any
information anywhere. Anyone know?

I've also researched the archives here and jotted down a few book
titles, but am interested in any historical novel recommendations
pertaining to the Sephardic Jews of late 15th century/early 16th
century Spain and also Venice (around the time of the Spanish
Inquisition).

THE MOVIE:
Secret Passage is a striking period piece featuring star acting turns
by Katherine Borowitz as Isabel, John Turturro as Paolo Zane, Tara
Fitzgerald as Clara, and Hannah Taylor Gordon as Clara's daughter,
Victoria. The Inquisition of 1492 forces Jewish sisters Isabel and
Clara (having taken on Christian names and posing as Catholics) to
flee Spain for Holland. When Clara's husband is killed helping other
Jews escape the Inquisition, the sisters flee again, this time to
Venice. There, Isabel negotiates their final escape with the Turks,
who agree to give the family safe passage to Turkey if Isabel uncovers
and hands over the secrets of Venetian glassmaking. To this end, she
and Clara infiltrate Venetian society, but Isabel's plans go awry when
the romantic and headstrong Clara falls in love with a mercenary
Venetian nobleman.

THANKS IN ADVANCE!
Tracy Marks