  We investigate a scenario that the top quark is the only window to the dark
matter particle. We use the effective Lagrangian approach to write down the
interaction between the top quark and the dark matter particle. Requiring the
dark matter satisfying the relic density we obtain the size of the effective
interaction. We show that the scenario can be made consistent with the direct
and indirect detection experiments by adjusting the size of the effective
coupling. Finally, we calculate the production cross section for $t\bar t +
\chi \bar \chi$ at the Large Hadron Collider (LHC), which will give rise to an
interesting signature of a top-pair plus large missing energy.
