Spy tunnel discovered behind potted plant in Transformation Class

What happened

During and after Transformation Class, Dash repeatedly noticed a potted plant in the corner moving. After class, the plant was found wobbling with someone or something behind it. Investigation revealed a hole and what looked like a tunnel, freshly dug, leading out beyond the school's boundary wall. Dash, Rob, and Ellen followed it but found no sign of which way the diggers had gone.

Resolution

The tunnel was discovered but the intruders had covered their tracks; no sign of which way they had gone.

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