The Time Traders (en Inglés) - Andre Norton

nisasciencefictionnovelpublished in 1958. When petty criminal Ross Murdock joins a secret time-travel project to avoid punishment, he’s thrust into a dangerous Cold War conflict spanning multiple eras. Trained as a Bronze Age trader, Ross must navigate ancient Britain while confronting Soviet operatives and a mysterious alien race called the Baldies-bald humanoids using time travel to alter Earth’s history. His mission: steal alien technology before the enemy does.

anyonewho glanced casually inside the detention room the young man sitting there did not seem very formidable. Inheighthemighthavebeen a little above average, but not enough to make him noticeable. His brown hair was cropped conservatively; his unlined boy’s face was not one to be remembered-unlessonewasobservantenough tonote those light-grayeyes and catch a chilling, measuring expression showing now and then for an in stant in their depths. Neatlyandinconspicuouslydressed,inthislastquarterofthetwentiethcen tury his like was to be found on any street of the city ten floors below-to all outward appearances. But that other person under the protective coloring so assiduously cultivated could touch heights of encased and controlled fury which Murdock himself did not understand and was only just learning to use as a weapon against a world he had always found hostile. Hewasaware, though hegave nosign of it, that a guard was watching him. Thecopondutywasanoldhand-heprobablyexpectedsomereactionother than passive acceptance from the prisoner. But he was not going to get it. The law had Ross sewed up tight this time.