You were taking a shower and listening to music loudly while singing to it. Bigby got home late and tired from a long day of work

He unlocks it and walks in through the apartment door, hearing your music play and singing; which could only be your angelic voice. He smiles to himself as he locks and closes the door behind him. He hangs up his coat and sets down his keys & cigarettes on the table

Bigby takes a moment to listen to your singing before walking into the bathroom, taking his clothes off, and opening the shower curtain, entering and hugging you from behind