Fans of Mina Wentworth and Rhys Trahearn rejoice. Mina Wentworth and the Invisible City is a wonderful short story that is a great addendum to The Iron Duke, giving us a little peek into life after the book ended. The Invisible City takes place 8 months after The Iron Duke. When a mutual aquaintance of Rhys and Mina's shows up dead, Mina is called in to investigate. The only clue they have is that the butler saw a giant brass wheel in the garden moments before the body was found. The hunt escalates when Mina discovers that the killer may have a connection to Rhys and she must find him before he can kill again.I actually didn't know about this novella until my paperback copy of The Iron Duke showed up in the mail. I originally read an e-copy from the library but I loved the book so much that I wanted a copy for myself. I am so glad I bought it, too, because it contains this great little novella. Short stories ar not usually my favorite. It's really hard to write a short story that feels complete in such a short span of words. But Brook manages it quite well with The Invisible City. The story arc felt complete with a true beginning, middle, and end and it was a fun visiting these characters again and getting another view into their world.The mystery plot was well executed and fast paced. Mina is as determined as ever and is dogged in her pursuit of the killer. While the mystery was a large part of the story, we also get to see how Mina and Rhys are taking to marriage. While they love each other passionately, their marriage is not without its problems. Both Rhys and Mina are still getting accustomed their new relationship. Neither of them has ever been in love before and they each have their own insecurities about the marriage. As a police inspector, Mina is often in danger, and Rhys is having a hard time dealing with his fear for her. Her safety means everything for him but he knows that he cannot stifle her or he will lose her. Mina is afraid that now that Rhys has her, his passion may have waned after the initial excitement of the pursuit has worn off. It was interesting to see how these two dealt with their feelings and insecurities. It's clear that they both love each other passionately. Of course there was also a good amount of steamy sex in this story - more than I would have thought for such a short story. I could have done with a wee bit less shagging, but I'm not really complaining.It was also great seeing some old favorites from The Iron Duke. Scarsdale is as charming and outrageous as ever. Newberry plays a large role as well and I loved seeing him again. Mina and Rhys also include Anne the tinker in their family and we learn a bit more about her in this story. I had a great time catching up with these characters. If you wondered what happened to Rhys and Mina after that fateful afternoon in the square, look no further. With incredible world building, great characters, a sexy romance and a fast paced mystery, The Invisible City has something for everyone. A must read for fans of The Iron Duke!