"It all comes down to probable cause: If you think something's up, maybe you gotta take a look"

This quote by Ron Livingston is describing the principle of possible cause, which is a legal requirement that must be met in order for police to carry out a search or make an arrest. Simply put, if a policeman has a reasonable suspicion that a crime has been committed, they should have possible cause to search or arrest somebody. The quote is suggesting that if you have a suspicion that something is wrong, then you must act and examine even more. This might mean that if you have a feeling that something is off, you ought to take the time to check out it and see if there is any proof to support your suspicions. Eventually, it is important to remember that if you have a suspicion, it is necessary to make the effort to investigate more and make certain that you have adequate evidence to support your suspicions.