Three thieves who stole 160 rare books more than a year ago by rappelling down the skylight of a warehouse in London continue to evade police, leaving a series of mysteries in their wake.

Sometime between Jan. 29 and Jan. 30, 2017, the three thieves bored holes into the warehouse’s skylight and rappelled down about 40 feet (12 meters), evading motion-sensor alarms. The books they stole included volumes written by Isaac Newton, Leonardo da Vinci, Nicolaus Copernicus and Galileo Galilei. Experts estimated the total value of the 160 books at around $2.5 million, the Guardian reported.

At the time, media outlets around the world dubbed the three individuals the “Mission Impossible” thieves, named after the movie franchise whose main character, Ethan Hunt (played by Tom Cruise), uses the same technique to get inside buildings. [Cracking Codices: 10 of the Most Mysterious Ancient Manuscripts]

More than a year after the theft took place, Live Science talked with a number of experts to see if any of the “Mission Impossible” thieves had slipped up and revealed their identities, or if the books had reappeared.

The thieves (like the movie character), it seems, have done a good job of concealing their identities and the location of the stolen books, leaving nothing but a series of mysteries in their wake.