This episode was the first one to have a full colour starting credits but then wasn't used for Deep Heat but was used again for In search for the Tajmanon onwards.

Also the alien ship is the same one from The ghost of the sea.

I know the reason for Thompson being in the state he is. When he's laid out in sickbay with Shore, Troy and the Doctor, there is a shot from Shore's point of view as the Doctor turns and talks to him. In this shot you can see Thompson's feet. Look at the toenails! He must be in agony!

Fisher must be especially susceptible to influence. The nurse, Atlanta, the doctor, Commander Shore, and Marina were all attended to personally, but Fisher got knocked out at a distance. Actually, if this were possible, why didn't Thompson just wipe out the entire hospital staff and patients in one shot?

Will it ever occur to anyone that it might be useful to teach Marina Morse code? (Not to mention sign language.)

Why didn't Marina stay by the radio and wait for Troy? It was actually rather touching that she would go to sit at her rival's bedside, but it just meant that she got locked up.

Apparently the watch was transmitting a constant, inaudible hypnotic tone, since Thompson immediately woke up when it broke. Why did it need a louder pitch to put the people in the initial trance?

Once again, Stingray blows an enemy vessel out of the water without finding out WHO THE ENEMY IS! It would be helpful to know for the future, wouldn't it?

How the heck does Thompson climb up the side of the control tower to hypnotise Shore?