An idealistic young man (Grant) is about to marry a wealthy socialite, but begins to fall for her spirited, black sheep sister (Hepburn).
For Cary Grant and Katharine Hepburn, 1938 was a vintage year. That said, the 'all-time classic' status afforded screwball comedy Bringing Up Baby has overshadowed the stars' subsequent pairing a few months later in George Cukor's Holiday.
Admittedly, this story isn't as continuously hilarious as the former, but its comic dissection of the unhappiness of the idle rich is brilliantly sharp, adding depths (emotional bullying, alcoholism) that make most rom-coms look like thematic pygmies in comparison. The writing is as sharp ("When I find myself in a position like this, I ask myself what would General Motors do? Then I do the opposite") as the timing with which it is delivered, and Hepburn is simply scintillating.
It's almost every bit as sharp as Bringing Up Baby, but odds-on you'll see that film first. Suffice to say that this is highly recommend further viewing in a similar vein.