Most certainly under-rated on IMDb: I'd put it on par with the previous episode "Forest of the Dead", a fun (and fascinating) psychological horror episode that explores beautifully the dangers of an echo chamber, mixed with a whole lotta fear. My eyes were popping out trying to imagine wtf was wrong with the people on this ship: constantly turning on whoever didn't agree with the consensus, but then again, fear has a way of overloading one's senses and the behavior of these passengers is certainly plausible. I can't help but think that Donna might have been very helpful in this scenario, somehow...damn her sun-bathing! Top 10 for the Tenth Doctor.