his/her/their accomplice
Tom y su cómplice estaban armados con fusiles de asalto.
Tom and his accomplice were armed with assault rifles.
Estaré preparado para ella y su cómplice.
I'll be ready for her and her accomplice.
— Pacto de sangre (1944)
El primero que levante la vista del plato ése es su cómplice.
The first one to look up from his plate—that’s his accomplice.
— El espinazo del diablo (2001)
Descubriré a Bi Yen Ju Li y su cómplice.
I will uncover Bi Yen Ju Li and his accomplice.
— El tigre y el dragón (2000)
Tom se negó a contarle a la policía quién fue su cómplice.
Tom refused to tell the police who his accomplice was.