Episode 1 (Being Human series 1)

IGN gave the first episode an 8.6 rating out of 10, saying that "[the makers of the show are] definitely off to a great start and have already presented us with a very intriguing universe".[1]

Russell Tovey (George) and Dylan Brown (Seth) were the only cast members from the pilot episode to renew their roles for Series 1. The roles of Mitchell, Annie, Herrick and Lauren were all recast. This was partially due to the longer-than-usual waiting period between pilot episode and formally committed series (resulting in some of the original actors becoming unavailable) and partially due to a shift in tone for which other actors were better suited. Compared to the pilot, producer Matthew Bouch described the series as "less gothic and slightly more rooted" as well as "a bit funnier"; he also described the series as "kind of a reboot" of the pilot.

These factors resulted in a distinct change in tone from the pilot episode. Annie (now played by Lenora Crichlow) was an ostensibly sunnier and more scatterbrained character than had been suggested by the more awkward, dour characterisation from Andrea Riseborough in the pilot; while Aidan Turner's take on Mitchell was more relaxed and smooth in presentation. Most notably, the recast Herrick (originally played by Adrian Lester) was altered in multiple respects including speech style, race and general demeanour. Originally an elegant, reserved and stylish vampire monarch, the new portrayal by Jason Watkins reinvented Herrick as a pudgy, avuncular middle-aged vampire working as a police sergeant, with a friendly manner masking a vicious streak.

Although Flotsam and Jetsam is the first episode of Being Human (and for most long-term viewers, the set-up episode to the show) it was preceded one year previously by a pilot episode, later titled The Monsters Within. Series creator Toby Whithouse has stated that he considers the story and events in The Monsters Within to be canonical, even though the production style and casting were noticeably different. The events of The Monsters Within precede those of Flotsam and Jetsam by an unspecified period, but probably no more than days or weeks as Mitchell's killing of Lauren and its immediate aftermath is still relatively recent.

The cold open of Flotsam and Jetsam restated, in a highly compressed form, several events and plot elements either shown or referred to The Monsters Within. These included the attack which infected George with the werewolf condition (and his subsequent transformation) and Mitchell's attack on Lauren. It also introduced elements not covered in The Monsters Within, including Mitchell's own recruitment into the vampire world by Herrick and greater illustration (via montage) of Annie's experiences of loneliness, resentment and disaffection following her own death.

Several scenes from The Monsters Within were recreated or adapted for the main body of the episode. These included the scene in which Mitchell warns off Seth from entering the hospital (which was mostly unaltered) and the scene in which Herrick notifies Mitchell of the coming vampire takeover and the need for Mitchell to pick a side (which was scripted, staged and played with an entirely different tone and no longer involved Lauren).

Some of the other events and scenes which took place in The Monsters Within were neither recreated nor referred to in Flotsam and Jetsam. Notably, there was no attempt to restage the initial meeting of Mitchell, George and Annie (the main episode began with all three relatively comfortably established as housemates), George and Mitchell's original application for jobs at the Bristol hospital, or Herrick's sumptuously staged address to the vampires in the Bristol basement. Some of the content of the latter (which was now too grandiose for the new conception of the character) was reworked into dialogue within "walk-and-talk" scenes between Herrick and Mitchell in and around the hospital grounds.

The subplot of George's abandonment of his former girlfriend Julie and her attempts to confront him over it (which had been central to The Monsters Within) was jettisoned. It was not denied or explicitly contradicted over the course of the subsequent series, but nor was it ever referred to again, and Julie would not return to the series. George would refer only in the most general sense to those he'd had to leave behind, and viewers would not encounter anyone from George's previous life until Daddy Ghoul (the sixth episode of Series 3, which focussed specifically on George's parents). The abandonment of this subplot also meant the loss of a significant scene in which George confronted Julie's abusive new boyfriend Peter and succeeded in intimidating him while also holding off his own werewolf urge to kill and eat.

Abandoning the Julie story also meant not recreating the climactic sequence in The Monsters Within (during which Julie confronts George in his safe room just as he is due to transform, unaware that she is risking her life, and in which Annie has to intervene to save Julie). This sequence had established Annie's conquering of her own ghost-fear (presented as being similar to agoraphobia) of leaving her own place of death. Annie's development of greater confidence and abilities, including the ability to leave her home and travel further afield, was developed at a slower pace over the course of Series 1.