Narrated by David Attenborough
Patrolling off-shore, powerful jet-propelled hunters cruise on deadly missions. Their intelligence is advanced. Their communication system is superb.
These 'extraterrestrials' are cephalopods - cuttlefish, squids and octopuses. Using their soft bodies they transmit pulsing colour patterns of staggering beauty that are much more than skin deep - they are a window on the living brain!
Yet there are difficulties in our understanding of these mysterious messages; they are in an alien tongue whose meaning scientists are only beginning to unravel. Can they speak to each other? Are they, perhaps, trying to speak to us?
BBC Bristol
(Subtitles on Ceefax page 170)