  At hadron colliders invisible particles $\chi$ can be inferred only through
observation of the transverse component of the vectorial sum of their momenta
-- missing $E_T$ or MET -- preventing reconstruction of the masses of their
mother particles. Here we outline situations where prior prejudice about the
event kinematics allows one to make the most of MET by decomposing it into its
expected sum of transverse contributions, each of which may be promoted to a
full four-momentum approximating the associated $\chi$. Such prejudice arises
when all $\chi$ in the event are expected to be light and (anti-)parallel to a
visible object, due to spin-correlations, back-to-back decays or boosted
decays. We focus on the last of these, with boosted semi-invisibly decaying
neutralinos widely motivated in supersymmetry (in the presence of light
gravitinos, singlinos, photini or pseudo-goldstini), and demonstrate our simple
method's ability to reconstruct sharp mass peaks from the MET decomposition.
