Hidden Side is a new theme released on August 1st 2019. It was unveiled by LEGO back on February 14, 2019.  The theme is focused around the haunted town of Newbury and is designed with an augmented reality (AR) app, allowing users to capture ghosts while solving mysteries within the spooky town.
The app will is to download from the App Store and Google Play. Even though the sets are based around an app, the sets are like any other standard system set, nothing has been shorted. At launch, the theme had eight sets.
There are plans to release more sets in 2020, but details have been withheld. 
- The theme uses unique stylized artwork for the boxes instead of the usual image of the set. The back of the boxes show the physical sets as well as the app feature.
- At the 2019 Toy Fair in London Hidden Side was shown to visitors in a hidden room under the name "The Hidden".