Mercay Island

Awaken on the shore of Mercay Island and speak with the fairy (Ciela) who explains Tetra was taken by the Ghost Ship.

Follow Ciela to Oshus's house and speak with him. He will direct you to the port to find Linebeck.

As you head east towards town, an earthquake collapses the bridge.

Return to Oshus's house and speak with him again. He tells you to wait for the bridge to be rebuilt.

Go to the cave east of Oshus's house.

At the far end of the cave, find a stone slab with palm trees. Write the number '7' on the sign to open the slab.

Open the chest revealed by the slab to obtain Oshus's sword. A book explaining sword basics is also present.

Speak with Oshus outside the cave again. He will scold you but allow you to keep the sword and offer swordplay lessons.

Head back to Oshus's house for swordplay instruction.

After your lesson, head north through the entrance to the Path.

Defeat the 3 Chu-Chus and continue north and east past the springy rock.

Perform a roll attack on the large tree to get a Red Rupee (worth 20 Rupees).

Head south, defeat more Chu-Chus, and slice through trees to enter a cave.

Inside the cave, clear the path by picking up and throwing three rocks.

Defeat 4 Chu-Chus past the locked door and open the chest to get a key.

Use the key to open the locked door. Defeat 5 more Chu-Chus in the large room.

Tap the block on the left side of the room to enter a chamber with 2 Keese. Read the sign: "When pulling the levers: First: 2nd from the left."

Head right, past another block, into a chamber with 4 Keese and a chest. Defeat the Keese, open the chest for a Red Rupee, and read the sign: "When pulling the levers: Second: 1st on the left. Last: 2nd from the right."

Go back to the large room and pull the levers in the correct order: 2nd from the left, then the far left, then the far right, then the 2nd from the right. Pulling them in the wrong order causes snakes to drop from the ceiling.

A key will drop. Use it to open the locked door and proceed up the stairs.

On the second floor, head down the path, defeating rats.

At the end, a key-carrying rat runs between two rat holes. To catch it, push the block in front of the nearest hole.

Let the rat run out, then ambush it as it turns back towards the blocked hole. Take the key.

Use the key to open the locked door and proceed past Keese to the exit.

Once outside, head to the port. You'll learn Linebeck has been missing for days.

Go to the Milk Bar on the western edge of town and speak with the bartender.

The bartender will tell you Linebeck was last seen heading towards the Temple of the Ocean King on the north side of the island.