Ludo was shocked that Liz wasn't looking properly into the mirror.
"But..but..you have to..." he stammered, pointing vigorously to the glass.

Then Professor Forrester came and told them to leave. Ludo scowled.
He let Liz drag him away and he mumbled to her..."Professor Pierce said we weren't out of bounds..."

But there was nothing he could do. He followed her out into the corridor. To the world outside the mirror.