From Here:
http://io9.com/steven-moffat-hints-the-doctor-will-lighten-up-in-docto-1689758843 The 49th Key
John Barrowman will produce and star in a miniseries adapting this new story from Erika Lewis. Here's a short description from The Hollywood Reporter:
The first chapter in an expansive fantasy series tells of a rogue archaeologist and a young autistic and mute boy on a treacherous journey through England to bring the boy home. The boy turns out to be the key to a gateway between our world and that of Enochia, a magical society that exists below the Earth's surface, filled with fantasy creatures and highly advanced humans.
The story makes its debut in issue 273 of Heavy Metal, which hits comics shops and bookstores Wednesday and is drawn by J.K. Woodward. The serialized story will run in the magazine through the year.