  We report the discovery with TESS of a remarkable quadruple star system with
a 2+1+1 configuration. The two unique characteristics of this system are that
(i) the inner eclipsing binary (stars Aa and Ab) eclipses the star in the
outermost orbit (star C), and (ii) these outer 4th body eclipses last for
$\sim$12 days, the longest of any such system known. The three orbital periods
are $\sim$3.3 days, $\sim$51 days, and $\sim$2100 days. The extremely long
duration of the outer eclipses is due to the fact that star B slows binary A
down on the sky relative to star C. We combine TESS photometric data,
ground-based photometric observations, eclipse timing points, radial velocity
measurements, the composite spectral energy distribution, and stellar isochones
in a spectro-photodynamical analysis to deduce all of the basic properties of
the four stars (mass, radius, $T_{\rm eff}$, and age), as well as the orbital
parameters for all three orbits. The four masses are $M_{\rm Aa}
=0.382$M$_\odot$, $M_{\rm Ab} =0.300$M$_\odot$, $M_{\rm B} =0.540$M$_\odot$ and
$M_{\rm C} =0.615$M$_\odot$, with a typical uncertainty of 0.015 M$_\odot$.
