。
I'm about to go visit a sick friend.
Literal
Friend [object-を] visit-sick [purpose-に] go point is.
~ところだ with a plain non-past verb (行くところだ) means 'about to do' — the action has not started yet. Contrast with ~たところだ ('just did'). 見舞い means a visit to someone who is ill or in hospital — not a casual social visit.