The concept of this online game was inspired by good old Atari game called Agent USA - if you don't know this title (which is hardly surprising) then take a look at the video below.
Basically the target was to, while traveling only using trains, to find a "fuzz bomb" that infects people and from time to time moves from one city to another within United States (again using trains only). Since the bomb's moves were limited by the railways available within game, with some experience, it wasn't that hard to follow it, also there were info booths spread in some cities, where we could learn the current location of the bomb.
In Where is Caroline? there are many ways to travel: you can walk between locations, take taxi, train, bus, plane - it all depends on what is available in the location you are in. Your goal is to find Caroline within 7 days, before she will get married and to convince her she is making a mistake (similar to finding the bomb in Agent USA). Just like the bomb Caroline is on the move, but the difference is her moves are not exactly random - since she is getting married in two weeks she has some things to take care of, so you have to find clues to where she could be and then locate her (which means being in right place at the right moment). Also, unlike Agent USA, in Where is Caroline? you have your limitations: forementioned time limit of 14 days, but also you need money to travel between locations and from time to time you have to get some sleep.
The game is fully played via Internet browser, so you don't have to install anything, all you need is any device with access to Internet.