What people look like

The Girl -- you have to describe her, because she's Young Halliday's love interest, and she's in danger, and young Halliday has been telling Blake about her pretty much since the start of the book. We first see her in a moment of high tension -- as Blake and Halliday step into the room,

"Marion Latimer stayed motionless, a tense figure in the candlelight; and the Shadow seemed to tremble at her feet. She had that thin, classic, rather cold type of beauty which makes face and body seem almost angular. Her hair was set in dark-gold waves next to the somewhat long head; her eyes were dark blue, glazed now with a preoccupied and somehow disturbing quality; the nose short, the mouth sensitive and determined."

Buried in that paragraph is a description that young tad could have written. Dark - gold waves of hair, a short nose, dark blue eye, a mouth.But there's more, isn't there? First of all, this is certainly Blake's dispassionate description, not that of an ardent young swain. More than that, she is at this point still a potential suspect in the murder that has yet to be committed, so we get the suspicious descriptive phrases -- the cold beauty, the disturbing quality to the eyes -- as well as the reassuring ones -- the sensitive and determined mouth. The point is, Carr wants us to fix her -- not so much the blue eyes, gold hair and short nose as her -- so he lingers over her introduction. In fact, he goes on longer --

"She stood there crookedly, almost as though she were lame. One hand was thrust deep into the pocket of The brown tweed coat wrapped around her thin body; as she watched us, the other hand left the window sill and pulled the collar close round her neck. They were fine, thin, wiry hands."

In the same scene, we next meet Halliday's aunt, who, like Marion, has been falling under the spell of the enigmatic charlatan Darworth, and like her, will fall under suspicion For Darworth's murder (I warned you there'd be spoilers). We see the aunt's white hair, her face like a wax flower -- which is wonderfully descriptive but wouldn't help you pick her out a lineup. We learn that her eyes were gentle -- and hard. Again, a description that could suggest her as innocent -- or guilty. Mostly, though, Carr refers us to "people who are supposed to look like eighteenth century marquises by Watteau. Lady Anne Bennington looked like a thoroughly modern, sharp-witted old lady got up to resemble one. Besides, her nose was too large."

You can say someone looks like a Watteau (or like a Dali, but that would be weirder), or that someone looks like John Cusack or Annette Bening, but you can't do it too often, because it's kinda cheating, and it signals to the reader that you're really not very good at this sort of thing. Like Carr, put it in a context, and like Carr, don't do it too much.