Investigate is the skill you use to find things out. It’s a counterpart to Notice—whereas Notice revolves around situational alertness and surface observation, Investigate revolves around concentrated effort and in-depth scrutiny.
Overcome:
Investigate obstacles are all about information that’s hard to uncover for some reason. Analyzing a crime scene for clues, searching a cluttered room for the item you need, even poring over a musty old tome to try and find the passage that makes everything make sense.
Racing against the clock to collect evidence before the cops show up or disaster occurs is a classic way to use Investigate in a challenge.
Create an Advantage:
Investigate is probably one of the most versatile skills you can use to create an advantage. As long as you’re willing to take the time, you can find out just about anything about anyone, discover nearly any detail about a place or object, or otherwise make up aspects about nearly anything in the game world that your character could reasonably unearth.
If that sounds broad, consider the following as just a few of the possibilities for using Investigate: eavesdropping on a conversation, looking for clues at a crime scene, examining records, verifying the truth of a piece of information, conducting surveillance, and researching a cover story.
Attack:
Investigate isn’t used to make attacks.
Defend:
Same here.