Investigative Play

Solving the Mystery
Sitting in the Red Dragon Inn one evening, drinking a fine ale and sharing memories of your last dungeon crawl you say, "Then around the corner comes the biggest..."
You are interrupted by a gruff voice, "Excuse me, good sirs, but I have a most urgent problem I am hoping you can help me with." says an elderly gentleman in a pointed hat standing over your table. "It seems my apprentice has gone astray. Young lad 'bout this tall," he indicates with his hand, "I sent him to fetch some fresh bat guano yesterday and he hasn't returned. It's most irregular, yes, most irregular. I will gladly pay for your time, and any expenses, if you will locate his where-abouts and of course render any rescue service he might require."
Once the shine of killing monsters starts to fade, the glitter of found gold ceases to gleam, maybe a nice investigative adventure is what your party needs? The investigative adventure brings into play an entirely different set of player and PC skills. Combat becomes secondary and role-play is usually given a more prominent part in the game as PCs question witnesses and seek to gather information. Observation and research skills, which can be useful when preparing for a dungeon crawl or searching for that hidden door, become more important in an investigative adventure where acquiring hidden knowledge is the main objective.
The investigative adventure is also an opportunity to get better acquainted with one's surroundings. The PCs may want to take special note of people, places and things nearby. They may want to visit depositories of information, such as libraries, a local sage or churches. Making contact with, and perhaps forming a relationship with, the local people of importance who can not only help with the situation at hand, but can become resources for the future, can be an important outcome. An investigative adventure can be a great way for the referee to show-case all the development work he/she has done on their world.
Mixing in the occasional investigative adventure not only helps keep things fresh in a campaign, it gives players an extended opportunity for in-character role-play and helps players learn more about the referee's milieu. It also gives the player who rather fancies a fast-talking, charismatic type character a chance to shine. And it also presents the referee an opportunity to cast some quite nasty villains and for the party to make some interesting enemies (who may re-appear in a future adventure).
Refereeing an investigative adventure is a bit different than a dungeon crawl, but can be quite fun if you enjoy role-playing the NPCs. One hard-earned piece of advice is to avoid dead-ends. When PCs fail to follow the clues, and they will, find creative ways to get them back on the trail. Failed investigative rolls should mean extra problems for the party, but not a dead-end. Sometimes a nice smack with the clue-by-four is in order.
Chaosium's Call of Cthulhu is the game that taught me about investigations and incidentally, about role-play as well, but there is no reason why White Box or any other rule system can't be used to run an investigative adventure. Investigative play gets players thinking, using logic and thinking outside the box. In a hobby that is all about creativity, this can only be a good thing. So the next time an opportunity to hunt down a missing apprentice comes your way, go for it!