Thief

The Thief is not a single character but a Black Market customer type: a shady seller who walks in with stolen goods and says “Take a peek and don’t ask questions.” Thieves only sell to you. Everything they offer is marked as stolen, which makes it cheap to buy but risky to keep.

When do Thieves visit?

Day 13. A scripted Thief comes during the early story visits, the same day the Mentor’s note about stolen items arrives.
Random visits. Black Market customers are drawn from a pool in which the Thief is one of several types (with the Shady Merchant, Petty Thief and Food Thief).
Weekly. The Safe Hands perk (Black Market reputation 40) guarantees a Thief visit once a week, on days that leave remainder 1 when divided by 7. It also improves the goods of every Thief.
Evidence Locker break-in. The event of the same name sends a special Thief who sells you a single stolen evidence crate.
Supplier visits. When a Display Case sign calls a seller of food, household goods, materials or medical supplies, the seller is either a Scavenger or a Thief. The odds follow your Black Market reputation against your Lower Levels reputation.

What does a Thief sell?

A regular Thief rolls independently for each item, and the chance of each item grows with your Black Market reputation (about 1.75 times at 80, 2.5 times at 100). Possible stock includes:

Luxury and trade goods: Bottle of Spring Water, ETERNAL Rejuvenation Serum, SYNC Neuroactive Perfume, L’ESSENCE Pheromone Perfume, Stack of Scratcher Tickets (5), HydraTech Micro Water Purifier, Advanced Water Filter, Advanced Turbo Booster.
Disposable keycards for Command, Security, Medical, Engineering and Service.
Modules: random performance, efficiency, quality, overclock, eco and fineness modules.
Medicine: a genuine injector, sometimes.
Loot crates (evidence, medical, engineering and others) once you have the Safe Hands perk.

The supplier-type Thief sells cheaper everyday stock instead. For food it can offer Nudka, Galaxy Blend and Raw Meat (Standard). For household goods: Box of PAX Tampons, Box of REX Condoms, AquaScan and Meat Cleaver. For materials: Electronic Parts (Common) and Gun Parts. For medical goods: Blood Bag, Rubbing Alcohol and Oxymore Injector.

What are the risks?

Every item a Thief sells is flagged stolen and carries a Heat value. Higher Heat means Security is more likely to find the item in an inspection, and selling stolen goods is recorded as Possession (Stolen Goods) in your Security record. Do not place heavily stolen items in the Display Case: it can trigger an extra inspection. See the Security guide and Store appeal.

FAQ

Is the Thief a story character?

No. The same name is used for several different visitors with the same job.

Do Thieves buy anything?

No. In the code they only sell; you cannot sell goods to them.

How do I get thieves to visit more often?

Raise your Black Market reputation. At 40 the Safe Hands perk guarantees a weekly Thief.