As the artificial hosts continue to dominate within the park, it’s apparent that humanity might have an ally in an unexpected Achilles Heel.

Another bumper-length episodes (71 minutes) the new series really hits in stride in this fourth episode. Its greatest strength is in its ability to surprise and wrong-foot you, and there’s a couple of occasions this week where you say ‘Whaaaat?!’ and then kick yourself for not picking up the clues. We’re in Delos’ high tech home, with a great performance by Peter Mullan as the park’s financier. Young William comes to visit and we’re immediately perplexed that he has to establish a baseline for fidelity. But why?

This is very much William’s episode, more than compensating for his absence last week, and we get to see his older incarnation (Ed Harris’ Man in Black) show just what a ruthless killer he is, and what he has learned from his annual trip to the park. Teddy made the right moral choice in releasing the fort soldiers the previous week, but now William has to clear up the mess.

Meanwhile, poor Bernard is in a bad way. He’s starting to glitch due to extensive cortical damage and loss of fluid. This is a theme across the episode, that the hosts are not entirely stable (well, duh!) but never so overtly, and while this may be an exploitable weakness, makes them more erratic and dangerous in the short term.

There’s a lovely moment where a character makes a surprise reappearance, and while the identity of a certain character at the end of the instalment makes you gasp, it’s to the writers’ credit that the clues were there all along.

Verdict: Beautifully-crafted cerebral TV that impresses rather than confuses, and still has time to surprise you and throw in a gunfight. 9/10

Nick Joy