We present the solution of the problem of heavy particle dynamics in a Fermi liquid environment which is asymptotically exact in a strong coupling limit. It is based on a path integral method and transforms into the self-consistent kinetic equation of Josephson and Lekner only in the case of weak scattering potential (small scattering phase shifts). In the general case the mobility can not be obtained by iterations of the kinetic equation. The theory explains the puzzling difference between the positive and negative ion mobility experiments and predicts rather unusual thermodynamic properties of ions in normal He-3. An enormous renormalization of the electron bubble effective mass, M(Bubble) greater-than-or-equal-to 10(4)m3, is predicted below the superfluid transition temperature.