Now and Then and Then Again by Sage Thomas

You arrive at the City, hub of galactic trade and politics, intending on enjoying your vacation and excited about getting a chance to explore the history you're studying. However, you soon find yourself far closer to that history than you'd thought possible, as you and your friends find yourself embroiled in conspiracies and mysteries dating back millennia.

As you fall deeper into the web, can you save your friends, let alone the world?