In this study, host and parasite populations whose generations are non-overlapping are modeled by difference equations. The effect of immunity on the model is investigated qualitatively. Many forms of complex dynamics are observed, including (a) non-unique dynamics, meaning that several attractors coexist, (b) basins of attraction with fractal properties (pattern of self-similarity and fractal basin boundaries), (c) supertransients, (d) attractor crises, (e) chaotic bands with narrow or wide periodic windows.