Can not remember this show .it was about some kids trying to find pieces of a power source of some kind jumping from place to place maybe in time don't know but the only way they could know they found it was by seeing it's reflection in a mirror of some type and then it glowed bright . It was a key of power or something . All I remember is they started the jumping in a cave and it ended two minutes later. For them no time had passed. In the end one kid was given a small piece.

I got the answer (Into The Labyrinth, UK, 1981)