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The Sinking City: Quid Pro Quo Main Case Walkthrough

Quid Pro Quo is a main quest in The Sinking City that follows right after “Lost at Sea”.


Go to the Archives of the Oakmont Police Department.

Use the case:
The Fate of the Expedition

Select those criteria:
Crimes: Violent Crimes
Subjects: Suspects
Evidence: Instruments of Crime

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Evidence found:
Police Report No 19-0451

In the report, there is an address. Go to this location at the Fish Market.

 Fishmarket-Map---Quid-Pro-Quo-----Sinking-City-2019 camzillasmom.com

Enter the market and the conversation will start. Talk to Anna. She’s the one in front of the “eye” poster.

Evidence collected:
Anna’s Request
Oakmont is starving (Mind Palace)
EOD is giving away fish (Mind Palace)

In the Mind Palace, combine:
Oakmont is starving <-> EOD is giving away fish

Go to the location and talk to the guy in front of the storage building.

 EOD-Fish-Storage---Quid-Pro-Quo-----Sinking-City-2019 camzillasmom.com

Evidence collected:
The Guard’s Testimony
A Key to the Fish Storage

Go down to the basement and use “Mind’s Eye”. Look at the dead fish and animal and activate the vision.

 Dead-Animals---EOD---Quid-Pro-Quo-----Sinking-City-2019 camzillasmom.com

Evidence collected:
The fish is poisonous

You will get a ghostly vision to follow. Follow it to a fish pile on the floor at ground level.

 Fish-Pile---EOD---Quid-Pro-Quo-----Sinking-City-2019 camzillasmom.com

Look at the fish pile and investigate the bottle.

Evidence collected:
Lab Flask

In Mind Palace, combine:
The fish is poisonous <-> EOD is giving away fish

The vision rift will open at ground level and you can put the events in order:

First the event at the fish box:

 Vision-1---EOD---Quid-Pro-Quo-----Sinking-City-2019 camzillasmom.com

Then the event at the fish pile on the floor.

 Vision-2---EOD---Quid-Pro-Quo-----Sinking-City-2019 camzillasmom.com

Then the upstairs event.

 Vision-3---EOD---Quid-Pro-Quo-----Sinking-City-2019 camzillasmom.com

Last one is at the stairs.

 Vision-4---EOD---Quid-Pro-Quo-----Sinking-City-2019 camzillasmom.com

Evidence collected:
The events in the Fish Storage
A mention of a professor (Mind Palace)

In the Mind Palace, combine:
A mention of a professor <-> Lab flask

Evidence collected:
The Poisoner and the University

Now go down the basement again and activate “Mind’s Eye”. There is a hidden passage close to the locker.

 Hidden-Passage---EOD---Quid-Pro-Quo-----Sinking-City-2019 camzillasmom.com

Look at the tools on the table.

Evidence collected:
A secret chamber in the warehouse

Talk to the guard outside and ask where the University is.

Evidence collected:
The Guard’s plea
The Guard is afraid of Anna (Mind Palace)

Return to Anna at the Fish Market and talk to her. Next stop University.

When you arrive, the door has a big “closed” sign on it. Talk to the guy next to the door. He sends you to the “Department of Medicine”, which is at the south of the biggest University building. Talk to the receptionist.

Evidence collected:
The Student’s Request
A key to the lab

Stay on ground floor. Behind the receptionist there is a “EOD is banned” poster on the wall. Look at it.

 EOD-is-banned---University---Quid-Pro-Quo-----Sinking-City-2019 camzillasmom.com

Evidence collected:
EOD is banned!
The EOD ranks are swelling (Mind Palace)

Go down to the basement and clear it. Talk to the receptionist again.

Evidence collected:
Westerbrook has access to poison.

You received the key. Go up the second floor now. Melee the door with the locker on it and go inside. Inspect the medicine cabinet and activate “Mind’s Eye”. Follow the ghost to Dr. Cavendish’s office and inspect the soap bar at his desk with Mind’s Eye again.

 Soap---University---Quid-Pro-Quo-----Sinking-City-2019 camzillasmom.com

Evidence collected:
George Cavendish made a spare key (Mind Palace)

Go to Mind Palace, combine:
George Cavendish made a spare key <-> Westerbrook has access to poison

Evidence collected:
The Poison Thief

Go to the City Hall and use the archives.

Choose Evidence:
The Poison Thief

Select criteria:
Subjects: Citizens
Registry: Citizen Records
District: Advent

Evidence collected:
George Cavendish Profile

 Apartment-map---Apartment-of-Cavendish---Quid-Pro-Quo-----Sinking-City-2019 camzillasmom.com

Go to the second floor and melee attack the lock on the door to get inside. Go to the bedroom/office. There is a piece of paper on the desk.

Evidence collected:
The Professor’s Fact List

Look at the pin board next to the desk and collect all you can.

Evidence collected:
EOD’s suspected crimes

Go to the Mind Palace, combine:
EOD’s suspected crimes <-> Secret chamber

There is a door with a lock on it. Melee attack to open and get inside. Activate Mind’s Eye, pick up the empty picture frame and reveal the vision.

 picture-frame---Apartment-of-Cavendish---Quid-Pro-Quo-----Sinking-City-2019 camzillasmom.com

Enter the vision rift and put together the events:

First the one at the table with the ring.

 Vision-2---Apartment-of-Cavendish---Quid-Pro-Quo-----Sinking-City-2019 camzillasmom.com

Then the one in the kitchen.

 Vision-1---Apartment-of-Cavendish---Quid-Pro-Quo-----Sinking-City-2019 camzillasmom.com

Last the one by the door.

 Vision-3---Apartment-of-Cavendish---Quid-Pro-Quo-----Sinking-City-2019 camzillasmom.com

After the conversation…

Evidence collected:
The poisoning was sabotage
Anna’s pregnancy was ordained

Go to Mind Palace, combine:
The poisoning was a sabotage <-> EOD ranks are swelling

Now combine:
Gearge sabotaged the EOD <-> The poisoned fish is spreading
Select your path
I selected: A desperate saviour

Return and combine:
Anna is pregnant <-> The guard is afraid of Anna

Now combine:
The EOD helps prevent famine <-> A zealous servant of EOD
Select your path
I selected: A filthy liar

Now I combine:
The EOD’s operations are shady
A desperate savior
A filthy liar

Talk to George, choose your path. I chose: I’ll help.

Evidence collected:
I can report George
A Full Flask of Ricin
George Cavendish’s Request

You can now go to either poison the rest of the fish, or report to Anna. I did report to Anna, since poisoning innocents isn’t my thing.

Talk to Anna.

Evidence Collected:
I reported George to Anna
High-Ranking Member of EOD

Go down the basement of the fish market. The entrance is next to the two guys who are looking at a map. Fight the men.

Evidence collected:
Note to Maurice

Exit the basement. After the conversation: Go back to Mr. Throgmorton.

Case Closed

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It all began in the ’80s when I was just 7 years old. Starting with basic arcade games, I soon delved into titles like Loom and Monkey Island by Lucasarts. Throughout the years, as I indulged in more and more games, I consistently sought clear guides to swiftly navigate my gameplay. Now, it’s my turn to contribute back to the community.

About The Sinking City

Release: June 28, 2019
Developer: Frogwares
Publisher: Bigben Interactive
Official Website: https://frogwares.com/