Unlucky thieves who have encroached on the treasury of the house and are detained by the guards temporarily end up in the basement. You can see the thieves caught from the Real Estate & Repair → List of Homes page, the "In the Basement..." link at a particular home.
Every house with a development level of 3 or higher has a basement.
Basements vary in size from house to house, and the number of thieves you can hold at one time depends on this. How many robberies your house can be subjected to, as many bandits you can place in the basement at one time.
The thief will be in the basement for two days, during which he will not be able to go on the case...
The homeowner can punish the thief with elaborate exegesis and reward him with very unpleasant combat skills: Flogging Wounds, Dung Spirit, Chicken. Also, each spent punishment removes 10 units of criminal authority from the thief.
The number of possible penalties for each thief (for the current stay in the basement) is calculated by the following formula:
N = K / 0.05,
K - the size of the house treasury at the time of the thief's capture.
For example, if the house treasury was equal to 1 gold coin, then you can punish the thief: N = 1/0.05 = 20 times. If the house treasury is less than 0.05 gold coin, you can't apply penalties to detained thieves (although they will still sit in the basement for two days, or until you release them sooner).
Any combination of punishments can be applied to a single thief, one punishment can be applied several times.
Executions ("Flogging Wounds" (whip), "Dung Spirit" (dip in dung pit), "Chicken" (smear with honey and sprinkle with feathers)) will be displayed in the newsfeed and cause great inconvenience to the thief in subsequent battles...
A thief who does not want to spend two days in the cellar can offer you a ransom in gold coins, which you can accept, and the thief will be released immediately.
You can also demand a ransom for moral displeasure yourself. You can use in-game email to communicate with the prisoner. The prisoner offers the ransom amount, if it suits the owner of the house, he orders the guards to let the hapless gentleman of fortune go. The homeowner transfers 5% of the amount of this buyout to the state budget.
If the thief has already offered you a ransom, but you decide to punish him first anyway, the ransom offered will be returned to the thief in his stash.
You can only detain big thieves (with knowledge of warfare equal to or greater than the value you specify), and you can automatically release smaller thieves. You can also set up automatic acceptance of a ransom equal to or above a certain amount. These values can be changed in the house-specific basement settings (Safety and Security page).