The third episode, guest-starring Kevin McNally, pulled in 4.18m (18.1%) for ITV1 from 7.45pm. The audience is down almost 1.6m on that for the first episode a fortnight ago.
Demons was beaten in the period by National Lottery quiz show In It To Win It, seen by 6.93m (30.1%) on BBC One, and Casualty, which had 6.53m (28%) from 8.30pm.
Before Demons, You've Been Framed! had managed 6.1m (28.6%) and Harry Hill's TV Burp had taken 6.19m (27.5%).
The latest episode of Eurovision: Your Country Needs You - a talent search to find this year's UK entrant - brought in 4.65m (21.5%) to BBC One from 6.35pm.
Amir Khan's appearance on All Star Family Fortunes was seen by 3.95m (17%) on ITV1 from 8.45pm, then a screening of Ocean's Twelve appealed to 2.37m (11.3%).
A repeat of The Real Dad's Army had 1.46m (6.3%) for Channel 4 in the 8pm hour, then the latest Celebrity Big Brother update took 2.05m (9.1%). Snakes On A Plane, a comedy thriller starring Samuel L Jackson, kept 1.88m (11.7%) until midnight.
Five started with 961k (4.1%) for NCIS at 8.20pm, then an hour later, a new episode of CSI: New York brought in 2.32m (10.6%), outrating Big Brother for the period. A new Law & Order logged 1.18m (6.5%) from 10.20pm.
A History Of Scotland was of interest to 1.88m (8.1%) on BBC Two in the 8pm hour, then live coverage of the second snooker Masters semi had 1.55m (6.9%).
BBC One was a comfortable first place in primetime with an average audience share of 25%, up half a point on last week. ITV1 slipped from 18.8% to 17.3%, while BBC Two rose from 8% to 8.4%. Channel 4 recorded a share of 7.3% - up from last week's 6.6% - and Five was down 1.5 points to 5.7%.
Sky1's new live Saturday night series Noel's HQ got off to a shaky start, with 340k (1.6%) from 7.30pm and 17th place on the multichannel ratings chart.
ITV2's screening of American Pie: The Wedding picked up a decent 516k (2.7%) from 9pm, with a further 114k (0.7%) on ITV2+1.
> Click here to read our review of Demons episode three
Ratings data supplied by Attentional