Ken Knudson sits in his Downers Grove office and draws thick, black circles on maps, lassoing metropolises. On a nearby wall covered with maps of the midwest and the nation, stick-on flags adorn the communities where Knudson plans to open branches of Sybaris, the couples-only resort business he founded 16 years ago with a small motel and a few water beds, mirrors on the ceilings, and adult movies on closed-circuit TV.

Not that Chicagoans have exactly avoided Sybaris. While few may display the bumper stickers that guests are given, 25,000 couples escaped from the conjugal Posturepedic to the Sybaris resorts in Downers Grove and Northbrook last year, at rates ranging from $70 to $495, bringing in $4.65 million in gross revenues, according to Knudson. Mention an interest in Sybaris, and someone you know will admit, blushing and eyes averted, to being a repeat customer. Many of my acquaintances have volunteered details of their visits, uniformly described as blissful, to Sybaris pool suites. People you never would have suspected of going there. People who–let’s face it–are probably not good swimmers.

“I immediately started to research the market for Sybaris. Who would be our customers? Married couples.

“And who has in-laws?” He drops to a crouch, grinning . . . and says nothing. I suddenly realize he is staring at me, waiting for a reply.

“If” by Bread is quavering on the sound track as Knudson unlocks the first door on a tour of his Northbrook bungalows, which are tucked at the back of a five-and-a-half-acre property beside a forest preserve. There are no windows, and the lights are kept low. Once the eyes adapt, they register layers of thick shag on the floors, walls, and nightstands; mirrors set into the ceiling; Hallmark-inspired verse on the bureau; a fireplace that lights at the twist of a dial; a king-size, plush- topped water bed; and a seven-foot sunken whirlpool.

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Average guys and their better halves are Knudson’s target customers. He installed bidets in the bathrooms simply because businessmen won’t find them at the Marriott; and he placed beds at space-wasting angles just because no home owner would ever decorate that way.