Gerhard Visser's Spider Paste

Taking a compass from his pocket, Visser was pleased to discover it was not pointing north. Instead, it was pointing towards the door that the woman had exited. (...)(Slade, 45)

(...)Opening her fist, she looked at her palm and let out a little shriek as she dropped an object on the table.
A metal spider, an inch wide, lay there on its back its legs kicking in the air. It ticked like a watch.(...)
He slowly turned the knife, then dropped one of his cufflinks onto the table. He bumped the spider close to it and the cufflink moved slightly. "It's magnetic. Powerfully so, for something that size. (...)" (Slade, 57-58)

(...) Visser let the compass needle come to a rest. He'd circled this large, walled house and each time, the needle had pointed towards it, which meant the spider was inside-and the woman as well, of course. (Slade, 60)