In the novel Edit
Nothing is known about Nick's life prior to the rise of Gilead, or even after that. All that is really known about him is that he became a Guardian, assigned to the household of Commander Fred. Offred finds Nick attractive; he apparently returns her feelings to an extent. He approaches her in the house, alone, one evening after she slips out of bed and speaks with her, which is forbidden. Nick also escorts her to see Commander Fred in his study, the Commander trusting his silence, and drives them to Jezebel's.
After Offred's night at Jezebel's, Serena Joy secretly arranges for Offred to visit Nick in his rooms and sleep with him to conceive a child. Offred sleeps with Nick willingly. She quickly develops feelings for him and he seems to reciprocate. Offred opens up to him, telling him a great deal about herself and her life prior to Gilead. Towards the end of the novel, Offred believes she's pregnant and tells Nick, as the baby is almost certainly his. Nick seems both happy and saddened by the news as he will not be able to play an active role in the child's life. It is unclear if Offred is truly pregnant or if it is wishful thinking on her part.
When the Eyes come for Offred, Nick comes to her room to collect her, leading Offred to believe he has been an Eye all along, which she had secretly feared. However, Nick informs her he is actually a member of Mayday and that the van sent for her is here to take her to safety. Offred doesn't know if she believes him, and it is not confirmed if Nick is truly a member of Mayday or not. However, in the epilogue, it is mentioned that one Commander Fred Waterford - who may have been Offred's Commander - was arrested and executed by the regime in the early years of Gilead for harbouring an infidel in his household, who could've been Nick. This would imply Nick was indeed a rebel and helped Offred to escape, though what ultimately became of him is unknown.
In the Hulu series Edit
Nick is portrayed by Max Minghella. He is originally from Michigan and his name before the rise of Gilead was Nick Blaine. He had a brother named Joshua.