Having escaped the Family henchmen, Layton and the gang continues to pursue Dr. Allen.
Regrouping[edit]
Check the banana peel on the floor for Puzzle 098, which will net you a 
gardener sticker. Move south and Don Paolo will separate from the group to do something on his own, while Layton suggests using the railway station to return to Flatstone. While that is certainly an option, there are more puzzles to be solved if you take a longer route. Move south and talk to Dylan for Puzzle 099, after which he will say that almost everyone in Chinatown works in some research facility. Enter the toy shop and talk to Viv for Puzzle 100, which will net you a 
butler sticker.
Exit the toy shop and move south, then talk to Misha for Puzzle 101. Move east and enter the bookshop, then talk to Maya for Puzzle 102. Exit Chinatown, then move to the area behind the casino and talk to Hardy for Puzzle 103, which will net you the 
Hardy's Lunch errand. Move south twice, then talk to Raleigh for Puzzle 104, which will net you the Raleigh's Soccer Ball errand.
Move west and south, then talk to Inspector Chelmey for Puzzle 105. Move south and enter the arcade for Puzzle 106. Exit the arcade through the southern entrance, then move to the outside of the clock shop. Talk to Art for Puzzle 143. Now, move back to Southern Street, outside the hotel. Layton will state that Dimitri Allen probably has another facility where he stores the time machine he is building. Enter the hotel and talk to Becky for Puzzle 131, which will net you the 
Clean Up course.
Walk upstairs to reunite with Flora. She managed to return to the hotel safely with future Luke. However, Shipley delivered an important message to future Luke, making him hastily leave to take care of some urgent business. She says that future Luke did promise to rejoin them, prompting Layton to comment about his perceptiveness. He will be interrupted by a visiting Inspector Chelmey. Chelmey claims that he saw one of the victims of the explosion at the Polydimensional Institute while walking on the street, though it's probably just an uncanny coincidence.
A missing Luke[edit]
Go downstairs and Layton will automatically ask Becky about crossing the Thames. Becky's grandmother will mention about a tunnel underneath the river, which was closed down ever since the Family gained control of the area. She will tell us to talk to Segal, the man at the black market, for more information. Layton will notice that Luke wandered off, so before you continue the investigation, you'll need to look for him.
Exit the hotel and talk to the Family Goon to trigger Puzzle 107, after which he will say that he saw Luke running off to Flatstone Street. Move east, then north twice, then east, and talk to Luke standing by the statue. Luke will reveal that his father is getting transferred out of London, so this may be his last adventure with Layton. After the conversation, move west and south twice, then talk to Hazel for the Hazel's Gift errand.
Enter the arcade and exit at the southern end, then talk to Max for Puzzle 132. Move to the casino entrance, where you'll find the casino open! You can enter the casino freely now, so do so. Talk to Harold for Puzzle 138, which will net you the 
tutor sticker. Move forward and talk to Mark for Puzzle 141.
Having settled everything at Flatstone, move along the path to 
Chinatown until you reach the black market. Talk to Catanova for Puzzle 108, which will net you a 
cat sticker. Talk to Segal for Puzzle 109, after which he will tell you that the entrance of the tunnel is guarded by a special code.
The tunnel under the river[edit]
Move back to the Riverside Hill, then go down the stairs and go forward. Check the strange gate for Puzzle 110, which will cause it to open. The interior is slightly flooded, which explains why the scientists around town have wet pants. Mystery 10 will be solved. However, before you can continue, you will be stopped by Ward, who won't let you pass until you've solved 80 puzzles. If you were following the walkthrough, you should have over 100 solved puzzles, so you're free to go on.
At the exit of the tunnel is the imposing gate of the research facility. Can you infiltrate it and find the prime minister without getting captured by the Family?