Where do helium filled balloons go?

you know…when people let them go into the open air… I worry in bed at night about these orphan balloons…. (which to be honest is the only thing that has convinced me to show my face here…nevertheless)

do they end up orbiting space in a beautiful coloured rainbow type constellation?

or does the gas compress, deflate the balloon which results in balloon shrivel and many…copious even (when you begin to think about the amount of helium filled balloons that are being released into the atmosphere every day…) amounts of shrivelled balloons plummet to the earth and fall out of the sky in front of unsuspecting balloon shrivel victims?

or…something else?..perhaps? ...hopefully?