WARNING SPOILERS: Reviewers have heaped universal praise on Breaking Bad's return, calling it "marvellous, deranged and unsettling" and a "fitting, pulse-pounding beginning to the end".

Directed by the show's lead Bryan Cranston, the episode Blood Money is the first episode of the second part of season five that aired in the US overnight.

Just seven episodes remain in Vince Gilligan's near-perfect show about a cancer-stricken school teacher's suburban drug dream-turned-nightmare.

Blood Money picked up right where the first part of season five left things.

After another flash forward showed a machine gun-toting Walter White scouring his abandoned home for a ricin capsule, it cut to DEA Agent Hank Schrader after his lightbulb 'aha' moment on a toilet during a family get together climaxed the end of the first part of season five.

Much of the episode dealt with Schrader struggling to comprehend the information that Walter White - who he thought of as a pitiful family man - is actually drug kingpin Heisenburg, the man responsible for a flawless strain of blue meth that has flooded Albuquerque.

He had been chasing him for more than a year.

It also showed White's sidekick Jesse Pinkman struggling to comprehend the death of a child after a train heist turned ugly last season, and showed him distributing his take from the robbery - $5 million - through neighbourhood yards.

As is typical of Breaking Bad, the episode wasn't without its lighter moments: The best came from a made-up episode of Star Trek, told by Jesse's rambling, drug-addled friends Badger and Skinny Pete.

The show ended with a superbly orchestrated, handwringingly tense 10-minute stand-off between Schrader and White, as they confronted each other in a garage over a tracking device White found on his car.

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One reviewer called the scene so intense, "Twitter might crash".

Blood Money has been universally praised by reviewers, with a near-perfect rating of 99 per cent on Metacritic.

"The episode is as marvellous, deranged and unsettling as anything series creator/executive producer Vince Gilligan and his team have done," wrote Curt Wagner from the Chicago Tribune.

"The episode's thoughtful, deliberate pacing constantly builds suspense and dread," he wrote.

Christopher Lawrence from the Las Vegas Review Journal agreed, calling the episode "off-the-charts intense".

"It's a fitting, pulse-pounding beginning to the end of one of TV's all-time most stunning, visually arresting series," he wrote.

The Hollywood Reporter's Tim Goodman said the episode was "riveting from start to finish".

"It concludes with an extended scene that is written, acted and shot with the kind of magnificence that is at the heart of why the series is so exalted."

The AV Club's Donna Bowman wrote: "After all the anticipation about how great this was going to be, I'm frankly astounded about how great it is in ways I wasn't at all imaginative enough to anticipate."