If you’re a fan of the Indiana Jones films, you won’t want to miss “Father and Son,” a well-hidden optional objective in Great Circle’s Vatican City. It does require you to go a little out of your way, but you’ll be rewarded with an exclusive Adventure Book, a couple of Field Notes, and a small callback to the third Indiana Jones film, the Last Crusade.
To find “Father and Son” at all, you must complete the Fieldwork mission “A Nun in Trouble.” You automatically start this after your first meeting with Gina. The quest requires you to sneak into Vatican City’s museum via the Blackshirts’ campsite, then rescue Gina’s friend Giuliana from the top of the Borgia Tower.
As part of your reward for completing “A Nun in Trouble,” you’ll receive Giuliana’s Key, which also begins the “Father and Son” Mystery mission. As Giuliana tells you, this opens a nearby door in the Borgia Tower, as seen on your in-game map below.
At first, this looks like it might just be a shortcut, as the door leads to a balcony with a zipline that you can use to get back to the street. You’ll land directly outside the Fountain of Confession, ready to continue the main story.
However, there’s a second locked door near the zipline which holds the actual mystery. Open it with Giuliana’s Key to find a storage room where you’ll find a sleeping dog, a lazy cat, a locked safe, a Bandage, and piles of disorganized documents. One of those documents is a new Adventure Book that teaches the Throttle skill, which enables you to launch stealth takedowns at range with Indy’s whip.
To solve this Mystery, you need to get into the safe. First, open the drawer in the table in the center of the room to find the Italian Poem. The poem is irrelevant, but someone has circled eight of its letters: I, R, I, A, T, A, S, O.
Second, open the drawer under the nearby typewriter to find a second document, the Polybius Square Diagram. This provides a cipher for the letters from the Italian Poem, albeit one that doesn’t see a lot of use in video games.
In practice, the major stumbling block on “Father and Son” comes from the cursive writing on the Poem. It’s easy to mistake the final “O” for an “A,” which screws up the entire code.
When run through the Diagram, the circled letters become a 4-digit code:
I + R = 5
I + A = 8
T + A = 7
S + O = 3
The code for the safe is 5873.
Open it to find the Siwa Photograph, Junior Report, Office Photograph, and Senior Report. This gives you 60 Adventure Points for finding all 4 notes, and another 100 for completing “Father and Son.”
Indiana Jones and the Great Circle is now available for Xbox Series X/S, Xbox Game Pass, and PC via Steam.