You watch her swim naked in the acequia, that maze of irrigation ditches that thread the flood plain of the Rio Grande in Albuquerque. The water is cold. It’s early October. You know who she is. You’re not supposed to know, but you do. She smiles, nods, keeps swimming, breast-stroking against the lazy current.  Her clothes lie in a heap on the bank.

 Should you ask her why she swims in murky water that has to be loaded with debris? You’re glad she’s in the water and can’t easily get out. She has reason to be wary of you.

How does she get out? The acequia banks are sheer and muddy, with no holds. You see her getting out one day. She lets the current take her to a culvert, its opening screened with heavy mesh to catch branches, leaves, and God-knows-what. She drives a foot into the space above the culvert, grips an upright and scrambles, lizard-like, more animal than human until she’s on her feet, her body covered in red New Mexico mud. Her clothes are upstream and she walks slowly toward them. A gaunt form with sagging breasts and pleated ass.

She’s in no hurry. If someone were to come along, she would not care. She’s never cared what anyone thinks. You watch her slip baggy gray pants and a t-shirt over her muddy body. It’s madness to spy on her this way. What would people say if they saw you slipping from tree to tree, following your father’s aging mistress? You, with all your etiquette.

Over the years, has she followed you the way you’re following her? If you were someone’s mistress, you would. Does she follow your mother? You’d certainly be curious about the wife. Did she see your mother at lunch with your father’s boss’s wife? Hear your mother order a martini, and the boss’s wife order coffee? Did she see your mother’s hands shake so badly she was unable to raise the martini to her lips, and the untouched drink sit accusingly for the duration of the lunch?

If she saw this, she would know something important about your mother—her crippling insecurity, but also her beauty. Your mother is a stunner, and this woman is not. You hope it gives her a pang. You hope she knows that no man would ever leave a woman like your mother for a woman like her.

Pam Lewis of Albuquerque, New Mexico, is the author of the novels Speak Softly, She Can Hear; Perfect Family; and A Young Wife. Her fiction has appeared in The New Yorker and her nonfiction in Redbook and various newspapers