This film, part of the Orson Welles season at BFI Southbank, also screens on 17th and 25th July. You can find the full details here. I have written a feature about the drama both on and off the screen involving this brilliant movie here at the Guardian Film website.
Chicago Reader review:
The weirdest great movie ever made (1948), which is somehow always summed up for me by the image of Glenn Anders cackling "Target practice! Target practice!" with unbalanced, malignant glee. Orson Welles directs and stars as an innocent Irish sailor who's drafted into a bizarre plot involving crippled criminal lawyer Everett Sloane and his icily seductive wife Rita Hayworth. Hayworth tells Welles he "knows nothing about wickedness" and proceeds to teach him, though he's an imperfect student. The film moves between Candide-like farce and a deeply disturbing apprehension of a world in grotesque, irreversible decay—it's the only true film noir comedy. The script, adapted from a novel by Sherwood King, is credited solely to Welles, but it's the work of many hands, including Welles, William Castle, Charles Lederer, and Fletcher Markle.
Here (and above) is the trailer.