Strategic intelligence and observation

وَقَالَتْ لِأُخْتِهِۦ قُصِّيهِ ۖ فَبَصُرَتْ بِهِۦ عَن جُنُبٍ وَهُمْ لَا يَشْعُرُونَ

And she said to his sister, "Follow him"; so she watched him from a distance while they perceived not.