Isle of Ember
Now that we're on board Linebeck's steamship, use the stylus to plot a course to take us safely from Mercay Island to the Isle of Ember. The ship will automatically travel along that course, until you choose to replot the course along the way. This part can be considered a tutorial of sorts on controlling the steamship, since besides course replotting, we also have stop and go switches, and we can adjust our view by pointing the stylus to the left and right sides of the screen to rotate. Overall, though, there's nothing along this part of the journey that will challenge us in any way, so just relax for a bit until we reach the Isle of Ember.
Now that we've reached the island, Linebeck will stay behind while we go off looking for Astrid. Head south and to the east until we cross a bridge, then continue heading eastward, slaying whatever Red Chuchus happen to be in our way, then go northeast. Ciela will notice a skeleton lying on the ground at the top of a set of stairs to the right. Head up the stairs toward the skeleton, and the ghost of a person named Kayo will appear, telling Link and Ciela that he hid Astrid in a house near where we docked, showing us the location on our map. He will ask us if we will open the door for him, and then tell us the secret to opening the door is knowing the location of the three torches that are on this island. One torch is directly to the right of Kayo's skeleton, another is near a house in the village near the dock, and the third is on the north part of the island. Mark these locations on your map as you explore the island and find the torches. There's an electrified gate on the southeast part of the island that we can't open yet.
Now that we have the locations of the torches, head back to the village near the dock and enter the house where Kayo hid Astrid. Go down into the cellar, and suddenly the door will close behind us and we'll have to fight off a bunch of Octoroks. They're easily slain with the sword, after which the door will reopen. Head toward the other door, and Ciela will sense somebody behind it and hear footsteps. She will tell us to call out to her, so shout out anything into the microphone (Link will automatically say, "Hey, back there!" regardless), and the person behind the door will answer, identifying herself as Astrid and asking to be released. Now go over to the map that's near the door and, using the locations of the torches that we marked on our map, copy them onto the door's. It will open, and Astrid can come out and you can ask her about the Ghost Ship. Astrid will then tell us that the Ghost Ship had visited her island a few days ago and that she was hidden away for her safety, but she becomes saddened to hear about Kayo's fate. She will ask us if we want our fortunes told, which is what we want. Soon Linebeck will join Link and Ciela as Astrid looks into her crystal ball and then tells Link that if he wants to find the Ghost Ship, he must be prepared to fight with the very darkness itself. With Link's determination to rescue Tetra, Astrid tells him he must now go into the Temple of Fire to defeat the powers of darkness that haunt that place. Before we leave, Astrid will tell us that she's released the seal on the door to the summit (the electrified door seen earlier).
So now we head back the same way as we did toward Kayo's skeleton, but this time we go over to the once-electrified door and just touch it to open it. Up the stairs to the next plateau, we have an Electric Chuchu to watch out for and some Tektites hopping around. We can't kill the Electric Chuchus yet, but we can take care of the Tektites with the sword. Soon, as we reach the next plateau, Ciela will warn us about falling rocks from the erupting volcano, so as we head around clockwise on this plateau we need to watch out for the rocks. At the southern part of the plateau, we see a door flanked by two candles. Go to both of the candles and blow each of them out to open the door. We can now finally enter the Temple of Fire.