Demo walkthrough *** SPOILER ***
This walkthrough assumes you are using the default key bindings. And always remember ... SAVE YOUR GAME!
Alt - jump
Shift - fast
Ctrl - use
Space - draw/holster weapon
1-0 - change weapon
I - inventory/menu
C - crouch/submerge
Jump into the pool to your right to retrieve a poison kit. (To retrieve it, stand on it and press Ctrl.) Now hop on over to the other side of the room and locate the big block with nasty faces on it. Pull it once toward the center of the room. (To pull it, go up to it, hold Ctrl, and move back. To push it, hold Ctrl and move forward.) Pull it once and push it once to place it where you need it to get up on the place with the torch.
Hop on the block, then pull yourself up on to the ledge with the torch. Walk to the opposite edge and use the whip to swing yourself over to the other ledge. Walk into the little room and go up to the ladder. Press Alt to start climbing, then hold Up until you reach the top.
A short ways away is a fork. Turn left to pick up a little treasure; turn right to continue the adventure. Before you slide down, draw your Colt .45 (press "2"). After the second slide, turn to your right and shoot the scorpion before he can poison your attitude.
Walk a little further, but keep your gun drawn; don't use your lighter here. When you see a tinge of blue, look for the scorpion in the darkness and shoot him.
Walk up to the water's edge. Note the fish swimming in the water? They bite. You'd take forever to finish off these with your Colt, so draw your machete and take the plunge. Chase the fish down and kill all three. Once you're done, you can continue.
It should be mentioned here to not use your medicinal sprigs/first aid kits unless you're down to about 1/8 health or bleeding (your health indicator turns red). If you are bleeding, one kit will stop the bleeding and another will restore you to full health. Poison kits should be used as soon as the poison threat is gone (i.e. in case of two scorpions, kill both quickly, then administer a poison kit).
To your left is a sort of stairway. Feel free to explore the left of it and acquire a piece of treasure, but it isn't necessary. Along the right is a small slab low enough to the water for you to climb out on. Remember to sheath your knife first! Once out, turn left, jump, and haul yourself up on to the stairway.
You are now facing a large hole. Drop into the hole and come up on the other side. Walk out and stand on the little slab of rock above the lava.
The next bit is a jumping puzzle, complicated by the fact that you have to time the lava blasts. However, it's not very difficult. Just jump, haul yourself up, and repeat. Note the crumbling blocks in the middle; get a running jump over those, then continue running as the blocks fall into the lava. The last lava jump is really a swing; get your whip out and have some fun, but beware: a rock is coming to keep you from standing still and rejoicing. Quickly run forward into the nook and you'll be safe.
Follow the rock after it passes and turn left into a small room. Don't get the treasure yet! If you do, a scorpion will run out and bite you. So use preventative measures. Light your lighter, spot the beggar, go up to its hole, and give it several good lashes with the whip. Confirm that it's dead with the lighter, then collect your treasure.
Drop down the hole and go over to the switch block. Press it with Ctrl and note what happens, but also note that you are releasing two scorpions from the door to your left. Be quick with the Colt or machete to kill the beggars, then use a poison kit.
Go through the passage and note the scorpion across the lava. Kill it with a few quick shots from the Colt, then jump across the lava and go out on the dock.
Now it is a waiting game. You are waiting for the two sharks (let out when their cage's hatch was released) to find their way to you. Once they do, you shoot them. It's certainly safer than trying to use the machete.
Once you've shot the sharks, jump into the water and get on the staircase again. This time you won't be jumping in the hole, you'll be jumping on the boat. Grab the key from the casket. Go over to the large red doors, stand by the keyhole to the left of them, and select the key from your inventory.
OK, now you leave the temple and battle Russians to leave the island. As soon as you exit the temple, run into the tent and pick up the trauma kit. Once you've picked that up, hop in the jeep (go up to the driver's side and press Ctrl) and drive in the direction it's headed to a little nook. Climb up the ladder and turn right, but don't go any further.
It's now time to play Snipe-the-Russian(tm). Draw your 9mm pistol and walk forward about halfway. Shoot until all three Russians are dead. Then slide down the slope in front of you and collect your jeep. Drive it up the slope you slid down by going in the tire tracks. Drive it across the bridge and through the tunnel, stopping for some treasure if so desired.
As you exit the tunnel, the Russians blow up the bridge. Not to worry, though ... you're Indy! Just hold down Shift and stay aligned with the bridge and you'll make it over.
There are now three more spots with 3-4 Russians in each one. Stop the Jeep before each one. You can easily do them by charging the enemy and shooting your 9mm like a madman, then reviving yourself later.
There remains one tricky part between the second and third ambushes. In this one, there's a bit of a corkscrew down to the bottom. You have to do this in the jeep, and make sure you do it right! Just keep the jeep on the sides and gun it to give it extra centrifugal force on the more vertical sections.
Get past the last group of Russians, floor the jeep over the last rise, and Sophia will be there to save you. At least I think it's Sophia ...
Using this methodology I successfully passed the demo on Dr. Jones level without too much fuss.