I was very excited for this murder mystery tour, however it was really lacking polish.
First the good: the voice acting was great, the app was easy to use, and the story and dialog were well written.
Why it only got two stars: for the logical sequence for the mystery it was really pushing one person, however the correct killer made sense after the hints were revealed so this I would say needs a bit of work but was okay. Everything for the mystery was based on the audio, so that means that ALL of the locations we stopped at had absolutely zero impact on the story. We stopped halfway through and just finished up the excursion at a park without visiting any of the other locations. The locations were nothing special.... A bank branch in a strip mall, an incredibly average hotel, a Walmart etc. The locations aligned with the story but this would have been better suited to have things written to incorporate historic or local sites instead of your run of the mill locations. When you arrived at each stop it would ask you a vague riddle about the location and after three or four stops we just didn't care about them anymore and focused on the story.
We had a good time and it was a fun experience, but this is more of a phone app than an excursion. You didn't need to be at this location which is what we were looking for. For improvements I would recommend to tie in the story to local stores sites or stories, have more interaction with the local sites that are unique or historic or just turn the entire thing into an app. If you go the app route then hire an illustrator and make the mystery more interactive with videos, pictures of evidence, etc. That has more than just the audio.
Overall, it's not a bad idea but it just needs some work to polish things off. I would recommend making more of an interactive app and advertising content on youtube instead of trying to sell this as an excursion on viator.