How did Theobald Volker assist the Adlers in the novel, The Wind Knows My Name?

Theobald Volker, a retired military colonel, lived in the apartment upstairs from the Adlers. On the night of Kristallnacht, Volker dressed in his military uniform and carried his duty weapon as he protected Rachel and Samuel from the Nazis. Volker then housed Rachel and Samuel in his apartment, as Rachel tried to obtain visas for her and her son.