  We report on the first non-perturbative calculation of the scalar Yukawa
model in the single-nucleon sector up to four-body Fock sector truncation (one
"scalar nucleon" and three "scalar pions"). The light-front Hamiltonian
approach with a systematic non-perturbative renormalization is applied. We
study the $n$-body norms and the electromagnetic form factor. We find that the
one- and two-body contributions dominate up to coupling $\alpha \approx 1.7$.
As we approach the coupling $\alpha \approx 2.2$, we discover that the
four-body contribution rises rapidly and overtakes the two- and three-body
contributions. By comparing with lower sector truncations, we show that the
form factor converges with respect to the Fock sector expansion.
