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Admiral Nelson has accepted an assignment to deliver classified material to a secret research facility located under the waters of Loch Ness in Scotland. When he arrives, he learns from the sole survivor, MacDougall, that the Loch Ness Monster has destroyed the facility. MacDougall is prepared to accept the material and carry on the work, but Nelson needs to learn the fate of the scientists. Following MacDougall's guidance, he takes Seaview through a deep underwater channel and into the Loch.
Admiral Nelson apparently does not know Professor MacDougall on sight, since an imposter very nearly receives some highly classified data by pretending to be the professor. Fortunately, Nelson is careful enough not to simply hand over such data, but why were there no passwords? Why wasn't Nelson supplied with a photograph of the professor?