James Lees was drawn through a rift to the Other Side dimension in 1856. The physics of Earth's reality was leaking through and disrupting the Other Side. They sent a duplicate of Lees through to try to help correct this. However, he was exploited for his supposed psychic talents, conducting seances for the rich and famous, even Queen Victoria.
After the Lees doppleganger was killed in 1863, the inhabitants of the Other Side decided to take more hostile actions. The real James Lees escaped back to Earth before this happened, and the gorge where the rift was located got flooded when a temporary dam was blown up. The Fifth Doctor used the TARDIS to permanently seal the rift. Because time ran differently on the Other Side, James was only a few days older even though he had gone through the rift seven years before. (PROSE: Empire of Death)
Behind the scenes Edit
In the Historical Notes, David Bishop states that the character of James Lees was inspired by spiritualist Robert James Lees.