I do all my own and most of the family laundry and have learned a lot about removing stains. I learned when I was a kid and for years in young adulthood living without mommy and a wife.
Black chain stain? You're on your own, but... I'd try all the stain products in the cupboard, reading the label for the ones that tout grease effectiveness (as opposed to grass stain, wine, etc.) and never dry an item if the stain isn't removed. Air dry only - will give you another shot at stain removal rather than baking it in. I might try a citrus based hand cleaner I have at the laundry/utility sink and as an aggressive a brush as the fabric will tolerate. Be careful not to damage the fabric..
But what's this with "the wife's laundry" bit?