The Box Tunnel 20 massacre committed by Mitchell (Aidan Turner) and Daisy (Amy Manson) in this episode will have repercussions that carry through season 3 and even into season 4.
This episode marks the last appearance of the pink-painted Totterdown house that was the series' main setting for its first two years. The house is last seen (with Mitchell (Aidan Turner) leaning from a top floor window) from the inside of the Volvo as George (Russell Tovey) and Annie (Lenora Crichlow) drive away, heading for Kemp (Donald Sumpter)'s 'facility'. Annie - "we're not coming back, are we?"
Mitchell (Aidan Turner)'s rage driven massacre of 20 people on a train (the 'Box Tunnel 20') would go on to be the main plot driver for the next series, as well as also having repercussions in the Fourth Series.
The young chaplain Mark who unintentionally reveals Lucy (Lyndsey Marshal) 's surname to Mitchell (Aidan Turner) is the same chaplain who had attended Mitchell's bedside at the hospital in series 1, episode 6, Bad Moon Rising (2009). He is well aware of the existence of vampires due to the attack on Mitchell by Herrick (Jason Watkins)'s men on that occasion.
The song played during the last few minutes of the episode is Miserere, a setting of Psalm 51 (50) by composer Gregorio Allegri.