were about to
Estaban a punto de descubrir algo que nadie podía imaginar.
They were about to discover something no one could have imagined.
Estaban a punto de salir cuando llegué allí.
They were about to leave when I got there.
Tom y Mary estaban a punto de irse cuando llegó John.
Tom and Mary were about to leave when John arrived.
Estaban a punto de perder la paciencia.
They were about to lose their patience.
Estaban a punto de salir cuando llegó la llamada urgente.
They were about to leave when the urgent call came in.