Why. Convoluted #3

On her lover's bed the sheets are still damp, but her sweat is cold now, like her husband's avoiding eyes.
They had loved. She knew. But then they just...didn't.
They'd become Mum and Dad for the kids, then, over time, sex with 'Dad'? Just...no!
He'd found another. He'd changed. She knew it.
She'd taken another too.
Her naked lover, now no longer hiding, stared at the husband.
The woman peered into both of their eyes.
She knew that look.
Then she knew why her husband had a key to her lover's flat.
He had really changed. Now she knew it.