Peacemaker (novel)

Publisher's Summary
The peace and quite of a remote homestead in the 1880's american west is shattered by the arrival of two shadowy outriders searching for 'the healer'. When the farmer refuses to help them, they raze the house to the ground using guns that shoot bolts instead of bullets... In the town of Redwater, the Doctor and  Martha learn of a snake-oil salesman whose patent medicines actually cure his patients. But when the Doctor and Martha investigate they discover the truth is stranger, and far more dangerous. Caught between the law of the gun and the dadly plans of intergalatic mercenaries, the Doctor and Martha are about to discover just how wild the west can become...

Characters

 * Tenth Doctor
 * Martha Jones

Continuity

 * This is the second known time of DW in which the Doctor visits the wild west the last being The Gunfighters.