After young Mackenzie's father died suddenly, she inherited the family detective agency. Now, with the aid of her robotic butler Cromwell and her short but helpful assistant Funghi, she sets out to earn her reputation as the Touch Detective. She'll chase down a stolen dream, search for a missing person, and more, as she attempts to become well known for her detecting skills.

Touch Detective is an adventure game in the style of later Sierra adventure games such as Space Quest 6. Players navigate Mackenzie through various screens by touching the area where they want her to move. Mackenzie can interact with certain on-screen objects with another tap of the stylus - depending on the object, she may look at it, pick it up, talk to it (if it can strike up a conversation), or even touch it to see what it feels like. Mackenzie likes to feel objects to understand them, which is why she's the 'Touch' Detective. Mackenzie can also check and combine objects in her inventory.

The top screen of the DS always has a close-up of Mackenzie herself. As she talks to other characters, observes objects and so forth, the top screen will display Mackenzie's thoughts - so while she may say one thing to a person ("Sure, I get it..."), she'll be thinking another ("What was that? I wasn't listening!"). It can be interesting (and sometimes insightful) to see the contrast between what Mackenzie says and what she thinks.

Touch Detective features four different 'cases' for Mackenzie to tackle. After the first case is completed, players can also choose to take on the Bonus Case. In this case, there is no main story, but Mackenzie can choose to take on small requests from characters, as well as increase her Touch List, which records the feeling of particular objects in the game world.