The Dig is the fourth chapter of Uncharted 2: Among Thieves.
Nate and Sully arrives at Lazarevic's Camp. They drop down, duck behind a log and Nate pulls out a pair of binoculars to see what's going on. He spots Chloe and pans over to see Lazarević scolding Flynn for not finding anything in the past three months.
One of his soldiers then approach and exposes another soldier for stealing aritfacts from another site. Before letting his soldier explain, Lazarevic pulls out his knife, and jabs him, then tosses him into the water. Seeing how angry he is, Sully insists they ruin his day even more. He presses the switch, which blows up the compound they went through earlier. Lazarevic and his men, along with Flynn and Chloe, run off to inverstigate.
Nate drops down and attempts to make his way to Lazarevic's quarters. Since they have left a few sentries behind, Sully decides to cover for Nate, and discovers a sniper rifle. Before raiding Lazarevic's files, Nate disposes of each soldier in the camp.
He then searches Lazarevic's quarters for the journals and information of Marco Polo he needs to find the Lost Fleet. He sees that Lazarevic has files in every expedition to find Shambhala all the way back to the 1600s. As he reads through the journal, he realizes that the Cintamani Stone isn't really here in Borneo. According to what Marco Polo wrote in the journal, he never really had the stone. Sully asks what Lazarevic is looking for. Nate then realizes that he's probably trying to pick up Marco Polo's trail back to Shambhala because the stone is still there. He then phones up Chloe and asks her if any remains or bodies were found, to which she says no. Nate then figures out that Marco's men must be hidden within the caverns up in a nearby mountain. He then asks Chloe to meet them up there.
Unfortunately, right before Nate finishes up, they are confronted by Lazarevic's soldiers. Nate engages in a firefight with the soldiers, with Sully covering for him from overhead. After defeating all of the soldiers, the two proceed to the hidden caverns.
The two trek through the jungle and reach the entrance, with Chloe meeting up with them. The three of them head inside to begin searching for a clue. Inside they see over 100 bodies scattered around, and Nate notices that their teeth are all black.
They them come into a small room and stumble upon something of interest - more blue resin, which Nate discovered before. He picks it up and grabs a torch. He then lights it, and the whole room become bluish and they then discover blood on the ground. They decide to follow the blood stains to see if they lead somewhere. The blood trail ends at wall, which can be moved. Nate and Sully push the stones out of the way, revealing another passage. They head through the passage and stumble across the body of Skelzor holding a map of the Valley of Temples within Nepal, along with a Phurba Dagger inside. Nate explains that the Phurba is a ritual object from Tibet used to destroy spiritual obstacles. After looking at the map, they then realize that the Phurba is the golden passport Marco was talking about in his journal.
The three then head out. Chloe heads out first to make sure the coast is clear. When Nate and Sully climb out, they hear Lazarevic's men and proceed to escape, but is halted by Chloe, who points her gun at them and tells them raise their hands (trying to protect her cover). Flynn then appears while Chloe searches them and tells Flynn they came from within the caverns. She then pulls out the map and hands it to Flynn. He then tells Chloe to escort them to Lazarevic.
As they walk the two back to the camp, Chloe looks behind her to see if Flynn is gone, then takes out the soldiers. She hands Nate the dagger, kisses him and tells him to meet her in Nepal. The two are spotted and escape, running down the mountain side. They then get stranded along the edge, overlooking a stream far down below. As they are desperate for their lives, Sully explains to Nate that this is not worth it and insists on bailing out while he continues on to Nepal with Chloe.
With Flynn and the soldiers approaching fast, they two dive into the stream below and swim away to shore, leaving Flynn disappointed at the thought of losing them.
You start this chapter with only a few sentries left in the area. Try to be as stealthy as possible to get past them. Once you arrive at the house in the center you'll watch a cutscene. At the end of the cutscene, Nate will be spotted by some men and forced to take cover. Luckily, he'll be given an unlimited supply of grenades so stay near them. Sully will also provide him with some cover using the Dragon Sniper rifle. Watch your flanks and protect Sully when he asks for help. After about four waves, Nate will need to take out a tower with a turret. To do this, he will need to throw a grenade into it. Do not try to throw it in using the arch; instead aim at the open window behind it, and press R2 to throw it directly there.
After the tower is taken out, climb out using the remains and reunite with Sully. Find your way through the jungle and eventually find the opening to the temple. Now united with Chloe, enter the temple and drop down. Make your way past the bodies and into a room containing resin. With the torch, follow the blood trail into a small room where the trail ends. Press to get past the wall and continue into a new room. At the end of the room, you will find the Phurba Dagger and a map of the Valley of Temples in the hands of Skelzor. After getting out of the temple, you will trigger another cutscene. After that, run, jump and platform to the end of the area and watch the cutscene leading into the next chapter.