High-sensitivity photoluminescence excitation (PLE) measurements were performed on the deep In-related isoelectronic defect in quenched Si: In responsible for the $P$,$Q$,$R$ luminescence lines. A complex set of excited states was obtained. Combining the PLE and conventional PL results, we identify three electronic states 3.8, 11.4, and 36.4 meV above the $P$-line initial state. These do not form a hydrogenlike series. Localized vibrations are identified to give rise to one-and two-phonon, Stokes, and anti-Stokes sidebands of the electronic transitions.