1. Once the game starts, you'll be at the office. But there's nothing to do there for now, so leave. After another cut-scene, you'll be at the police station. Ask the policeman about a lead and you'll unlock a new location (Mum-Mum's car shop), as well as finding yo* first clue. You can also talk to Cough's head, in yo* inventory: eventually, you'll get another clue.
2. First, go talk to the “talking dead”. Choose all the dialogue options, and you'll unlock a new location (Zombino's bakery).
3. Go to the bakery, and enter by the main door. You'll overhear the two goons talking about Sewers Awk, and how they always forget the combination of his house's door. Talk to the goons to ob-tain a new clue, then leave the area.
4. Go to Awk's house, and try to open the window. It'll be impossible for Margh, so ask Ghvnn to open the window for you. You'll spy on Awk and you'll hear him talking about some new job he's taking care of, finding a new clue
5. It's time to visit Mum-Mum's car shop. Have a nice chat with him and you'll find two clues (Remember to ask him about a clue that's in yo* notebook)
6. Go back to the Talking Dead. Ask him about the goons in the bakery shop and you'll get a tasty juice of info about them that you can use later. Ask him about Mum-Mum, too, and you'll get a new clue. You can also ask him about Sewers Awk, and he'll remind Margh that he already has his phone number.
7. Visit yo* office, and open the left drawer below the archive. You'll find Awk's phone number. Before using the phone, though, ask Cough to talk in yo* stead. You'll get the combination to Awk's door.
8. You can now go to Sewer's Awk house once again, and open its door. After a cutscene, you'll have to inspect the room. Check both the drawers (you'll ob-tain some money), then the carpet. Ask Awk to move a bit, then check the carpet again to find another clue.
9. Go back to the Bakery shop. Use the money to buy a cake for Ghvnn, getting a new clue. Now talk to the goons and mention the information you received from the Talking Dead. They'll start fighting, and you can steal the key while they're distracted.
10. Go outside, and use the key to open the door right next to the shop. You'll find yo*self inside a new area. Pick up the explosives, inspect the guns, then the whole area to o*ain two clues.
You can now solve the case. Don't worry if there's a lone evidence that you can't combine, for now. If you choose the wrong solution, you'll have to guess again until you find the right one.
After that, you'll visit an old brain farm, where you'll finally find Cough's body. Try to use the explosives on the cell bars to ob-tain the last clue of the game Combine that clue with the only one that's left to form a second deduction. Use the gun on the lock to open the cell, and watch the “good ending” of the episode.