These tough to run in any game. Players have to rely on what you felt was important enough to reveal. When they go outside your clues, it can be obvious that you are improvising and thus render the information as a false lead. That said, I would make it a dramatic sequence. Consequences would include the authorities showing up, accidentally wrecking some evidence (contaminating the crime scene), stray animals/vermin showing up, bystanders that interfere or assume the heroes are guilty, allies of the victim, weather ruining the scene, servants sent to clean up, a looter taking key evidence, and "the building is on fire"(because John adds that to everything). OPPORTUNITIES might include finding a hidden clue, recognizing a unique wound, discovering a tattoo or emblem of am organization (victim's or assailant), noticing a bystander that is suspicious or may have been a witness, spotting a pattern with other crimes, footprints, and the infamous "item grabbed off the killer". Players may also need raises to get info out of witnesses, establish a timeline of the crime, convince the law they are there to help, calm a panicking witness, hide evidence, secure evidence properly, plant false evidence, or steal something. (Even the good guys do this from time to time)

I think Sal nailed it. A Dramatic Sequence for this is very appropriate. Different heroes can use different skills (Scholarship, Notice, Convince to question, etc.) to investigate, assist one another (before Dice are rolled and during the sequence), and unexpected things could occur based upon actions (Someone upsets a witness and they call in the guards, etc.)

Some of the opportunities listed above though to me seem like actual "Successes" (hidden clue, e.g.). I would recommend Opportunities be things like 'drawing a link between two clues' or 'spotting patterns in the clues'. You should have a list of all the 'relevant clues' and then have an opportunity for each that makes sense.

For example, the clue might be "The footprints were made by booted feet about the size of an adult male", but an Opportunity might give that the the person remembers seeing mud tracks at the manor house that match the tread.

John

That is a great idea for using opportunity in the scene. considered it borrowed.

I agree that using a Dramatic Sequence for this would work well.  I'd borrow a bit from Gumshoe system that I would say fitted well with both 2nd Ed 7th Sea and the swashbuckling genre - the core clues needed to solve the mystery in a scene should be available to the heroes just for being there.  The hero that finds the clue might be deteremined by using an appropriate skill or having an appropriate background.  Opportunities would give extra clues (like point spends do in Gumshoe) while consequences would be complications like a villain becoming aware of the heroes interest and arranging for a brute squad or two to be waiting where the clues point or the local watch deciding the heroes are stepping on their toes.