The Broad Faced Sac Spider is Trachelas tranquillus – I like to think of this as the “tranquil spider”. It apparently only comes into homes in the fall when it is preparing to hibernate. Indeed, the first time we ever saw this tranquil spider was in September when the leaves were starting to turn!
They look very much like other sac spiders, but their tail end is pale, where most sac spiders have darker tail ends. Their middle is dark, where most sac spiders have a lighter middle. So it looks like a “reverse” sac spider to us.
Note that they are tranquil – but I’ve read reports that, if agitated, they can bite with a painful bite that feels like a bee sting. So do not agitate the tranquil spider!
http://www.suttonmass.org/animals/spiders/