The strange Devises on the Enterprise

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My name is Carl Miller. I work as a special investigator for the US Navy. My rank is a Commander. I've been in the service for twenty five years and I've worked as an investagator for fifteen. In my years as an investagotor, I thought I've seen everything. However, last year I started to work on a case that has had me quite puzzled. It's a case that began over twenty years ago. It seemed that the aircraft carrier the Enterprise had an unusual visitor on board. He was someone claiming to be a Pavel Checkov from Starfleet. He spoke with a Russian accent, and was wearing civilian clothes.

At first glance, I thought that he was a spy. However, there were things that happened that are totally unexplainable. First how did he get on board a heavely secured nuclear powered warship without anyone else seeing him? Then, how did he after falling twenty feet straight down, rendering him unconscious and presuming to die, manage to contact cohorts to rescue him, then suddenly vanish? Then what in the hell were those devices found on him?

My assignment is to piece together this mystery and put together answers. So far no one has put together anything.