Mark Of The Octopus

S1 E4: Before Mike Nelson can investigate the disappearance of two geologists the sea washes one of them upon the beach, his body bearing marks apparently made by the suction valves of a giant octopus. When later the body of a young boy is found with the same mysterious marks, Mike is sure that the killer is a diabolically clever man who has somehow found a way to duplicate the mark of an octopus.