Here is the written walkthrough on this mission.
First, buy the mission and you will encounter the briefing.
You will see a gallery of Dosh’s Family, but mixed up.
Talk to the cleaner and rearrange the pictures into the correct place.
Every picture except Slosh’s will be there. Click on the right arrow to go to another room.
Talk to the librarian.
Type in Slosh like above when he asks you what portrait was missing. He will give you a book. Drag it into your backpack. After that click the drawers on the desk –
Put this in your inventory and notice the pile of books near the platform of which the librarian is standing on. Move the items you have just obtained to the sticking out pole (circle first) and it should look like this:
Click the board on top of the lever and you will see a kind of pinball flipper mechanic. Using the knobs, follow this picture then press ‘START’.
A hidden passage will open up. If you go over to this passage a scroll is on the floor.
Then, click the fireplace and then you will see a huge door, with 4 zeros. A frame is propped up in the corner. Take it and return to the gallery room. Place the frame into the missing slot and then drag the scroll to the picture.
EVERY SINGLE PICTURE IS DIFFERENT.
Count the shapes and make sure you include the overlapped ones. In my case it’s:
7 rectangles 
3 triangles /|
5 diamonds <>
5 squares [|]
If you recall, the fireplace had some sort of shapes on it. Go back and insert the numbers. If the code is wrong go back and count again. If not, the door should open. If you have been following the order I have been doing it, go back and click on the arrow at the bottom-most.
Open all the cupboards and Fridge. If the item has a white outline, click and drag it to the rings and bowls. Open your backpack, get your book and flick to the page where it tells you how to make a potion/freezing ray. You will see a full screen symbol. Click that and it should be like this:
Follow the instructions so you have a pink pan, a yellow pan and a blue pan. Place them on the fire and let the gauge go slightly over the green part. Then, put it back so the other liquids get cooked. Take it in turns so they all have ticks.
Quickly pick up the syringe and fill it up, one liquid each. Drag it again near the top of the funnel and repeat for the others. You should get this message:
Rememeber the code room? Go back to the place:
Go in and watch the video: (It’s quite funny).
Then, SHOOTING TIME!!!!
Shoot all of the guards with the newly obtained freezing ray. Try and hit the spider plugs. Soon the ice will melt so keep shooting. At the end keep hitting the big one on the middle of the room and then the mission will end.
Thank you so much for reading this guide! Sorry if there were to many pictures, I’m not good at writing. Thx a lot!