Here's an entire walkthrough, gonig through all of the different objectives, so you can get help on one specific thing instead of cheating on everything else just to be able to do one thing you couldn't figure out...
To complete the game you need to find the killer, get proof, and take him in.
To find the killer:
Find out what's going on with the crabs and follow leads
First lead:
Look at the crate that was in Arthur's hands
How to find out what's going on with the crabs:
Get the knife used to kill Arthur
Use the knife on the closed crates to the left of the dock screen
Take a good look at the crab and take one
This allows you to visit two seafood places
At the blue crab cafe:
Use an ID card
How to get an ID card:
Get the card on your desk
Get a fingerprint on the card
Get a picture and put it on the card
How to get a fingerprint:
Find the fingerprinting book in your office and use the knife on it
Follow the steps
How to get the inkpad:
Get a sea sponge from the docks
Get the squids to squirt ink(they squirt ink in defense, they're afraid of crabs)
Use the sponge on the ink
The rest of the steps are easy, but if you need further help on them, here it is:
Use the inkpad on Arhur's hand
Use his inky hand on the card
How to get the picture:
Use the knife on a poster to the right of the big door at the Blue Crab Cafe(while zoomed out from the door)
Use the picture on the card
Go in the kitchen and go out the back door to the alley, a thug will lead you to your guy. You need to prove he killed him and that he's counterfeitting the crabs.
How to get proof:
Listen in on his conversation from outside and record him, but you can't do that unless you somehow get rid of his bodyguard.
How to get rid of the bodyguard:
Go back to the Blue Crab cafe, go in the alley(the gate is open now)
Move one of the boxes on the ground, get the business card, and read it
Go to the other restaurant, Joe's Crab Shack, get rid of the rat, talk to him a little, and give him the card
How to get rid of the rat:
Make a homemade trap(how? here it is)
Find some bait(cheese) and use it with the toy crab(where can I find cheese? in the Blue Crab Cafe kitchen)
Use the trap with the rat
The thug is distracted by Joe calling him, make a homemade tool to listen in on his phone conversation and record it.
How to make the tool:
Get the can halves in the trash can near the door where the Boss is
Get some wire(help below)
Use the wire on the cans and use the listening device on the window
How to record it:
Get the victrola the Blue Crab Cafe chef is listening to to stop working(how? here it is) and take it
Use the crab with the power box outside, in the alley. The crab will spit on it and mess it up(there are the wires for the listening device, hanging down, get 'em)
Use the listening device with the victrola and use the recording device on the window, you've got proof!
Take him in! Oh no, he destroyed your evidence! He's trying to kill you, oops, you forgot to load your gun, improvise! Stabbings are too messy? Oh come on!(find a way to get him without shooting him or using the knife, use something else on him) You found out another way to prove he is the killer and he's dead now, you win!
| 
