Danger was already closing in, yet he remained totally oblivious.
Tips
memory
浑然 means 'completely, wholly' (as in 浑然一体 'a perfect whole'). Combined with 不觉 ('not aware'), the sense is 'utterly without awareness' — not just missing it, but absorbed in something else.
usage
Pattern: 对...浑然不觉 — 'totally unaware of X.' Often describes someone absorbed in another activity, missing what's happening around them.
