Remember Sam McGrew?

A bunch of the boys were whooping it up in the Malamute saloon;
The kid that handles the music-box was hitting a jag-time tune;
Back of the bar, in a solo game, sat Dangerous Dan McGrew,
And watching his luck was hi light-o’-love, the lady that’s known as Lou.
When out of the night, which was fifty below, and [...]

What does this phrase mean?

the phrase is:

So the stranger stumbles across the room and flops down there like a fool.

I need an explanation to what this means, it’s from the poem The Shooting of Dan McGrew by Robert Service.

Please help!