Complete Solution

Part One (the whole game!)

Open the front door of Eric's home and go inside. Eric will find that his family have disappeared. Pick up the dagger and note. Pick up the mat fringe (located on the right-hand side of the mat) and the mat. You will find a locked trap door. Go upstairs into the bedroom, pick up the pillow and pick up the half ticket to the fair which is underneath it. Try to open the drawers in the chest of drawers, all of which are locked. Look at and Talk to the mouse hole. Go back downstairs and outside. After the cut scene, walk to the path. Go to the beach and use your fishing rod on the sea. Eric will, eventually, find an old boot. Look at the old boot and find some money in it. Unfortunately, it's not enough for the ransom money. 

Go to the village and into the shop. Talk to the shopkeeper and ask for a fish and a roll of sellotape. Go back outside and notice the tramp with no shoes. Go back to the map and onto the circus. Give the fish to the seal, who will get off his stand. Pick up the stand to find another boot. Go back to the village and give the pair of boots to the tramp who will give you a paperclip in return. 
Go back to your home, and use your paperclip on the trapdoor. Slide down the chute to find yourself on the cellar floor, dazed but unhurt. Look at the mouse hole and pick up the matches and key that you find.  Open the barrel lid and use your matches with the open barrel (which I don't think contains Ale!) After your trip, go back inside your home and proceed upstairs. Use the key on the top drawer and pick up the other half to the ticket to the fair. Use the sellotape with the two half tickets and go to the fair.

At the fair, talk to the policeman and persaude him that you can look after the boy. Use the dagger on the boy's balloon which will burst, causing the boy to run away, crying. Pick up the string and give your ticket to the fair attendant. Go inside the fair.Once inside, talk to the man at the coconut shy. Pick up a ball - you will hit a coconut on your first attempt. Well done! Throw the coconut at the faulty balloon machine and pick up the balloons which come out. Use the balloons with the helium machine and then with the string to tie them together.

Go back to the village, and a rather snooty (and rich) man will walk on to wait for a bus. Use the helium-filled balloons with the rich man and pick up the money which leaves his pockets. Still not enough for the ransom? Don't worry, you might get some help with that soon.  
Go back to the fair and to the big wheel. Give the money to Stan Jnr. and open the door to the cart. After another flying journey, you will land on the island near to Corvée Island. Use the doorbell and go inside.  Ask the man inside about the things hanging up around his room. Ask him if you can have a look at them. Look at the window and the card on the window sill. Give the man the mat fringe and he will give you some home made cheese in return. Talk to the man again and say "Sorry to bother you". He will tell you how to get back to the main island. Outside, pick up the raised area and go down the hole. Eventually, you will reach the main island. 
Go to your home and to the bedroom. Use the cheese with the floor and talk to the mouse hole. The mouse will smell the cheese and run out. Pick up the mouse and partially eaten cheese and go to the Post Office in the village. Give the mouse to the cat, who will move away from the cards. Talk to the Post mistress and ask if the post office lends money. Despite her negative response, tell her what a nice jumper she is wearing and then ask her again. Flattery gets you everywhere, and she agrees to allow you to buy on credit. Pick up the card with a tree on the front (Look at the cards to find out which one this is) and pick up an envelope. Give the card to the Post mistress and take the card back to the man on the island (through the underground passage).

Give the man on the island the birthday card and talk to him again. Tell him about the ransom demand. Eventually, he will agree to lend you the ransom money. Take the money to the bridge (the Post mistress will appear, asking for her money) and put it down. The witch will arrive and take the money, without releasing your family. 
Go back to the man on the island, and tell him about what has happened. He tells you about his friend on Comble Island who may be able to help you. He will also eventually lend you his rowing boat. Take the oars and photo of Fergus. Go outside and use the oars with the boat. Well done, you've completed Part 1, and the whole game