Air platypus egg is hanging in a sock on a wire between the restaurant and the gift shop. Enter the balcony (the door in the middle of the location) - it turns out that the wire mechanism is without a crank. Travel to Doc's workshop and visit the room where you've faced the robot. Pick up the crank (bottom shelf, on the left side). Return to the Old City, place the crank into the mechanism, use it and take the egg from the sock.
Make your way to the captain's home and take a look at the bookshelf, dying flowers, aquarium by the window and the window itself. Each time, Rufus will automatically retrieve a memo written by the captain (in all, there are 5 of them). Leave the house and enter the door one floor below.
Talk with the Poet. Give him all memos written by the captain, and he will let you take anything from his belongings. Use the opportunity and pick-up the candle and a glass of water found on the window sill, an urn (shelf next to the Poet), charcoal (on the floor), bread (ledge on the right side of the room), and thread (above the door).
Make your way to Seagull and take a look at the bookcase. Click on the book that unlocks the hidden pathway, then enter the crow's nest. The mast is topped by hanging sleeves - to access them, you need to pour the remains (brr...) into the pipe. The mast will be lowered. You can now use the sleeve as a catapult for the egg, but there is still something missing - a hook to be exact. The hook can be found in the jar at the docks (next to the fisherman). Connect it with the lace and use it on the sleeves, then connect the other end of the sleeve with the hook on the pipe. Place the egg in the catapult. It will turn out that the catapult is still not tense enough, so proceed to the hidden pathway and open up the vault on your right. Use the vacuum to clean up the contents of the lint. Return to the crow's nest - the catapult is ready, but you still do not have anything to cut it with.
Travel to the tavern and make an attempt to take a razorfish from the wall - no can do, it has an installed motion detector. Take the sugarbowl from Bozo's table and pour the sugar into a generator in the location with the gondolier (above the entrance to the tavern). Enter the tavern again and pick up the razorfish. Before you make your way back to Bellevue, return to the area with the entrance to the tavern and proceed left. You'll reach Little Venice. Pick up an antenna found next to the building.
Proceed to the foretop and use the razorfish to cut the catapult. Take the sleeves and travel to Bellevue. There is an aviary next to the entrance to the market - put the bread in the feeder. The platypus will start to circle around the feeder. Create a landing net - mix sleeves and the antenna. Use the landing net to catch the platypus, then travel to the location with the gift shop and the restaurant. Place the platypus in the nest on your right.