Visitor in Blackwood Grove

A spacecraft crashes in Blackwood Grove, and the Kid is the only one watching. Federal agents hunt down the signal, but no one can get near the craft due to its crushing forcefield. Why can some objects pass through the forcefield, but others are repelled? Hiding in the craft, the Visitor hopes the Kid can figure out the rule before the Agents and help it escape. The Agents want to dissect the Visitor and keep the ship.

Experiment with what can pass through, figure out the rule, and win in this asymmetric game of teamwork and inductive reasoning.