The Great Holmes Keeps the Great Cthulhu in his House at Ry'leh
The path ends at a ledge that descends into the underground river. Something needs to be found to build a bridge across, and Holmes will ask Watson to find a mast from one of the wrecked ships nearby. The game will pass control to Watson who must turn around and find a nearby log. (It is directly behind you, near the stone. There are also a broken cask and crank nearby.) Walk back to the ledge, and select the log in your inventory. Use it on the ledge to create an instant bridge. The metal rungs on the other side of the make shift bridge provide a way up into the lighthouse. An unhappy visitor and buckets of poison gas will be waiting to greet you.
You must let Watson in, but do not stay long in the lighthouse. There is a bucket outside of the lighthouse, take it. Open the door and go outside to the wrecked building where you found the barrel of fresh water. By using the bucket on the barrel of fresh water, a bucket of water is created. Go back inside the white house to neutralize the poison gas. This is not an easy process as the host, a man named Ashmat will be shooting at Sherlock Holmes. Doctor Watson will provide covering fire for his friend while he neutralizes the poison gas.
There is a lever on the left side of the circle of poison buckets. Pulling the lever causes a crate to drop on the lone gunmen, but he will ascend up the stairs shortly after this scene takes place. Proceed into the next room once the poisoned gas no longer poses any threat.
There is a landing at the top of the stairs. Climbing the stairs reveals an interesting picture as well as a white panel with a strange pentagram symbol on it. Pick up the panel and take it to the pool of blood at the top of the stairs. You will need to draw the symbol in this picture on this panel using the pool of blood on the landing. Advance toward Ashmat and observe as Holmes uses the unholy knowledge that he and Watson have collected. Ashmat collapses and no longer serves as an obstacle toward your final goal.
Climb to the top of the light house. A door might slow your progress, but an iron bar removes this obstacle. Dirty Somers and his Hindu companion await you there, but there is another door that requires the key. Somers only says that the key is within his Hindu friend. Pick up a piece of paper from the table and the Directive of Sect appears in your documents.
You will be moved back downstairs automatically and be given another quiz. The answer to the question about where the key is hidden is in the stomach. Doctor Watson takes the saber rescued from the pirate gentleman and impales the Hindu man to retrieve the key. Take the key and go back up the stairs. Use the key on the door and enter the final room.
Lord Rochester awaits you there, and hooded men are on their way. You need to turn off the lighthouse light. Turn towards the light source. There will be a blue and green bottle on the floor. The green bottle is found on the left side, and the blue bottle is found on the right side. There is an empty bottle on the floor, pick it up and select it from your inventory. Place the empty bottle on the bottom ring while you are looking in the direction of the blue bottle. Turn the wheel so the blue bottle is on top. Take the blue bottle and turn towards the green bottle. Place the blue bottle on the bottom ring and turn the wheel so the green bottle is on top.
The light house turns on and Lord Rochester disappears. Once Holmes and Watson are far away from this scene, Holmes summarizes what happened and the two are ready for a little rest before their next adventure.