Kate Stewart and her UNIT team investigate and confront alien attacks on the planet Earth. Something is stirring, an old foe to those in UNIT with a long memory. And fortunately, to face an old foe... there are old friends.

4.2 Tidal Wave by Guy Adams
When an experimental tidal power generator needs its eco-friendly credentials checked, Kate Stewart calls in an expert.

Soon, Jo Jones is bound for 'Project Charybdis' in the South Atlantic, along with an awestruck Osgood.

But out at sea, a treacherous plan is set in motion to awake an ancient race. Beneath the seabed an army is sleeping - an army of Sea Devils!