When pigs fly.

The MASTER returns!
Captain Jack Harkness reunites with the Doctor and the TARDIS is thrown out of control to the end of the universe. They meet Professor Yana, who is working on a means to save the remnants of humanity while a race known as the "Futurekind" attempt to thwart his plans.

Download part one of this two-parter at Chaz' 2007 Dr. Who Episode Guide & Download Webpage

It's a real cliff-hanger!