Narelle Grech was a teenager when she first discovered that she'd been conceived using donor sperm. As her shock turned to deep curiosity, Narelle decided — she had to meet this man.

All she has to go on is his donor code, T5.

It leads her on a search that spans two decades, take her across continents and results in a landmark law that allows donor-conceived people to learn the identity of their donor — and vice versa.

Thanks to the ABC's Damien Carrick and Sarah Dingle for the use of archival interviews in this episode.