The Forgotten City (2015)

The Forgotten City is the first mod in history to win a national Writers' Guild award for its script. It is a critically acclaimed expansion mod offering a unique 6 - 8 hour experience: a murder mystery investigation set in an ancient underground city. You'll need to solve it using your wits, and the ability to travel through time...

Storyline

You must help a woman, Cassia, find her brother. When entering the city, you discover the Lake House. You must defeat Altruis's ghost for a key to this house. When entering the Lake House, you enter a time portal going back about 7 years ago to the time of Last Seed. You must find out what had happened to the city and find an exit out of it.