He held the rank of Commander and was the only one, besides Ambuscade's master Laurel Malachi, who knew how Bachfisch had managed to get warrants as naval auxiliaries of the Silesian Confederate Navy for both his ships.
When Bachfisch lost his two legs during the fight with RHNS Hecate, Gruber temporary assumed command. He saved the Havenite destroyer's surviving crew and sent Lieutenant Ferguson aboard the wreck to tackle its computers. After this, he managed to bring his severely damaged freighter to Sidemore to report Bachfisch's findings to Admiral Honor Harrington. After their arrival in the Marsh System, he urged Bachfisch to leave his ship so that his wounds could be attended to by Fritz Montoya. (HH10)