If you've followed the walkthrough so far, you should have three addresses; One for Sherman Street where the doctor's bill came from, one for West End St where Joey Seigal's car registration indicates he lives, and the map which indicates that Joe's Bar is on Peoria Street. You should start by checking out Joey's place. Ideally, you should have at least 12 coins before you leave if you want to get to every location and back without a hassle. Use the slot machine in the casino to earn more coins.
Hop into one of the two cabs waiting for you on the left end of Peoria Street (it doesn't matter which one, one driver is just a little nicer than the other), and ask to be taken to West End Street. He'll take you to your destination, and come to a stop. The fare will cost $0.75, so USE three coins on the "Pay Here" slot in the lower right corner of the cab scene. If on the NES version you don't have enough coins, or if you try to give the driver a $20, he will explain that the ride is free.
West End Street[edit]
Once you arrive, OPEN the front door of the building, and MOVE through it. You will enter a posh lobby of an apartment building. You will see an elevator in the distance with the word "Private" above it. If you examine the small object on the wall to the right, the game will indicate that it appears to be a slot for something like a card. You happen to have a card on you. If you haven't looked inside the wallet which is inside of the pocket of the coat you found when you began the game, do so now, and you will find a card. USE the card on this slot, and the elevator doors will open. Move into the elevator.
Once inside, you'll need to USE the card on the slot in the interior as well in order to get it to move. The elevator will rise and then the doors will open. MOVE out of the elevator, and you will arrive in a luxurious penthouse. You should examine all around the apartment. You will find one thing of interest if you examine the fireplace mantle. There's a picture of a woman with a new address on the back, S. Kedzie Street. You can TAKE this picture, as well as the magazine on the coffee table if you want, but there's no reason to.
MOVE to the bottom square in the Exits window to get back in the elevator, USE the card on the slot to return to the lobby, MOVE out of the elevator, and MOVE to the bottom square again to exit the building. Make one more MOVE command to get in the cab. This time, ask to be taken to S. Kedzie.
South Kedzie Street[edit]
Once again, pay the taxi driver with coins if you are able to, and MOVE out of the cab. You will arrive in front of a bungalow with an overgrown garden. If you try to OPEN the front door, you will find that it's locked. Furthermore, none of the keys in your possession will open it. You won't find a key for this home anywhere in fact, so you'll have to get a little creative. Try to USE your gun on the door. You will shoot the lock and blast the door open. Now you can MOVE inside.
When you step inside, you will notice the odor of cheap perfume. Once again, you must examine the place for clues. On top of the desk, you will notice two slips of paper and a pair of earrings. The earrings are irrelevant, but the two slips of paper both contain what appear to be safe combinations. TAKE them, and then OPEN the desk drawer. Inside the drawer, you'll find another key and a diary. TAKE them both. With the diary in your possession, you can OPEN it and TAKE the bookmark. Now you can examine the diary and read the contents. It appears that the woman who lived here was involved with Joey Siegal, but would prefer to be with wealth Mr. Sternwood who happens to be married.
MOVE out of the bungalow and back into the cab. There's only one place you haven't visited yet. Ask to be taken to Sherman Street at this time.
Sherman Street[edit]
When you arrive, OPEN the front door and MOVE inside. You'll have two options; head down the hallway or climb the stairs. Start with the hallway, and you'll reach the door to Dr. Brody's office, whose name appeared on the medical bill. If you try to OPEN the door, you will find that it's locked. USE the key you found in the desk of the bungalow (Key 5) to unlock it and MOVE into the office.
The office is deserted. You will see a medicine cabinet loaded with 12 vials of assorted medicine and a filing cabinet to the right. If you try to OPEN the cabinet, you will notice that it's locked. It claims to be a combination lock, so none of the keys you have will work, nor will either of the sequence of numbers you found on Kenzie Street. So you'll have to open it the only other way you know how; USE your gun on the lock. With the lock blown off, you will find four files inside the cabinet. Files 1 and 3 are just medical records, with the first file being about one Ace Harding. File 2 is interesting in that it's a bit of evidence that Joey Siegal ordered the medicine to be delivered to his office.
File 4 is really what you're after here. It contains a list of medications and the effects that they have. Of particular interest is Bisodiumits which is said to cure memory loss, and that more than one dose is typically required. Also notable is Sodium Pentothal, which makes unconscious people speak truthfully. At this time, examine the medicine cabinet, and TAKE every dose of Bisodiumits that you can find. Once you have them, choose to USE them with the syringe (or capsules in the NES version), and then USE the syringe/capsule on yourself. You'll have to perform these steps a total of three times before your memory is fully restored, and you remember that you are in fact Ace Harding, private detective.
Now that your memory is restored, you are no longer in danger of passing out and dying from the effects of the medicine. You're still not out of the woods yet, as things still look pretty grim for you, and you have yet to clear your name. Before you leave, there's one more thing you should grab; at least one vial of Sodium Pentothal. Once you have it, use MOVE to make your way out of the office, and back to the stairs. MOVE up the stairs, and you will arrive in front of what appears to be your office.
As you look through the glass of the door, you can make out a silhouette of a person waiting for you inside. If you paid the drunk on Peoria Street for some information, you may recall that Joey Siegal hired a hitman who may be waiting in your office. Attempting to find out who it is in a civilized fashion will in fact only get you killed. Your only option is to USE your gun and point it at the glass in the door.
Once you've done this, you still can't get inside because the door is locked. Thankfully, Key 5 is a Master Key to this building; using it can open the door to your office, as well. MOVE inside, and the dead hitman's feet will be visible from behind your desk. First, OPEN the file cabinet, and examine the files inside. One of the files is a letter blackmailing you into taking part in the kidnapping. The other two files are just notes on the woman known as Sugar Shack. (She's the one you may have met near the Police Station earlier) Take the blackmail letter. Then OPEN the desk to look inside the drawer. Inside, you will find an ammunition case. If you OPEN this, you will find six bullets. TAKE the bullets just in case. (If you want to reload your gun, you'll have to do it one by one. It's not the most thrilling gameplay. You'll only ever need one more bullet if you run into trouble past this point, though.)
With that, there's nothing left to do but to take the cab and return to Peoria Street. There are still two items that you have yet to investigate; the trunk of the car parked in front of Joe's Bar, and the combination safe in the office above the bar. Head back now to check them out.