The Triangle:

Cash-strapped newlyweds David and Diana Murphy (Woody Harrelson and Demi Moore), made an offer they can’t refuse by ethically challenged billionaire John Gage (Robert Redford)
 
Does It Get Complicated? 

The deal’s simple enough: Gage gets one night with Diana, the Murphys get $1 million.  Scarcely even counts as a triangle. 

But when David gets the hump about the, er, hump, things do downhill fast.  Clearly, he’s never the heard the one about mixing business and pleasure.  
Remember, kids, if you’re gonna sign a contract – keep emotion out of it.