Absolutely Inflexible

Time travel is possible, but only forward in time. Visitors from the past are multiple and dangerous as they carry deadly germs people of the future do not have immunity against anymore. So all the time travelers are promptly apprehended and isolated. The head of the institution responsible for isolation of the time travelers is implacable and absolutely inflexible in carrying out his duties. Until one of the time travelers gives him a device allegedly capable of moving people in time...