Torchwood plummeted to a series low on Thursday night, according to early overnight data.
Shedding 650k on last week's outing, the fourth series of the Doctor Who spinoff - starring John Barrowman - averaged 3.45m (14.1%) for BBC One in the 9pm hour.
However, due to interest in Channel 5's Celebrity Big Brother relaunch, it is likely that more viewers will watch episode six on iPlayer.
> Celebrity Big Brother is ratings smash for Channel 5
Nevertheless, Miracle Day has failed to live up to the heights of Children of Earth, which was aired night-by-night last year and attracted ratings of over 7 million.
Fellow dramas Single Handed and The Killing also suffered from the heavier 9pm competition, grabbing 2.79m (11.4%) on ITV1 (+1: 101k) and 987k (4%) on Channel 4 (+1: 196k), a respective drop of 280k and 180k.
Elsewhere, BBC One had 3.98m (17.5%) for a Crimewatch special at 8pm on the recent London riots, after which 3.53m (14.7%) caught a repeat of Traffic Cops.
Country House Rescue delivered 1.64m (7%) to Channel 4 (+1: 300k) and Cowboy Builders logged 1m (4.3%) for Channel 5.
Over on BBC Two, Monty Halls' Great Irish Escape mustered 1.17m (5%) at 8pm, and Town with Nicholas Crane had 2.04m (7.6%) at 9pm, while Channel 4 documentary Jaycee: 18 Years In Captivity interested 1.7m (9.4%) at 10pm (+1: 339k).
Overall, ITV1 led primetime with 18.1% (+1: 0.5%), beating BBC One's 17.6%. In third place, Channel 5 captured 11.9%, its best primetime share since 2000, while Channel 4 and BBC Two had 5.8% (+1: 0.9%) and 5.4% respectively.
