Ezio searched for the mysterious voice, descending down some stairs to a small landing and approached a set of stacked boxes. Leonardo appeared behind him, and Ezio turned around on hearing his footsteps.
Leonardo handing Ezio the list of Templar overseers
Ezio: Chi è lá? (Who is there?)
Leonardo:Ezio!
Ezio:Leonardo!
Leonardo:I knew you were behind the break-in at Sant'Angelo! It is good to see you, friend.
Ezio:Come here.
The two embraced.
Leonardo:Forgive me. The Borgia have commandeered my services. Actually, they would have killed me had I refused.
Ezio:What do they want?
Leonardo:War machines. I have constructed weapons for all the Borgia guards and other terrible monstrosities besides. They are very well designed, Ezio. Here. The names of the Templars overseeing their construction. Cesare intends to supply his army with my creations. You must dismantle them.
Ezio: Grazie (Thank you). I will take care of the plans and the machines.
Leonardo:There is far graver news, I am afraid. They have the Apple.
Leonardo:Wait here. I will be back soon. I must return to my workshop. Wait here.
Some time passed before Leonardo returned with the invention. Ezio gave him a pouch of coins and he handed over the gear. Ezio admired his acquisition.
Leonardo:I will wait nearby for a few more hours in case you change your mind.
He left to station himself elsewhere to avoid attention. Ezio headed to procure the missing money then returned. Leonardo sat down again and whispered to him.
Leonardo:What can I get you this time? What would you like me to make for you? Let me guess, you need more designs. What can I bring you this time Ezio?
Ezio reunited with Leonardo but learned the Borgia were forcing him to build war machines for Cesare's army. Despite this, Leonardo assured Ezio that he could remake the gear lost during the siege of Monteriggioni and arranged a secret communication method so they would know when and where to meet and exchange funds for equipment.
Just before Leonardo appears, Ezio approaches some stacked cardboard boxes. This is an allusion to the Metal Gear series character Solid Snake, who could hide from enemy guards in a cardboard box.
If the camera was manipulated to show Ezio's face when the voice was calling to him, it could be seen that Ezio was saying Leonardo's line.
Even if Ezio does not purchase anything from Leonardo, the Double Blade still shows up in the Inventory menu's Weapons section for the rest of the game.