The cover of book 3 for Daphne & Velma has been revealed on Amazon. The novel will once again be written by Morgan Baden, which makes me wonder if the first book's author Josephine Ruby was just a psuedonym Morgan was using. Note that Amazon still has the wrong date on their site, the correct release date is June 1, 2021, not February 2.
Here's the description for the final book:
There are a lot of secrets buried in the town of Crystal Cove. And the biggest case of all still remains unsolved... why did the town's original settlers all disappear? What happened to them? Velma is determined to find out... especially because her family's ancestors were among the disappeared. And now that she and Daphne have started to get a reputation for solving mysteries, everyone in town is looking to them for answers. But digging up the past can be dangerous... especially when some people in town have profited from the mystery for so long. Can these two intrepid teen detectives crack the case... and escape with their lives?