One of the Alliance commanders of the bioweapons division in the Unification War, Haymer gained a name for himself after the war for his collection of priceless and rare artifacts of Earth-that-was (he has "warehouses full of stuff"). During the War he would target populated areas with valuables, wipe out all life (being a bio-weapons expert) and then take anything of value left behind (Trash). After the War, Haymer used his wealth to buy a private floating island on Bellerophon ("Home to the rich and paranoid").
Haymer is one of Saffron's many husbands and Mal theorised that he is the only one she realy loved [Trash]. Haymer was left by Saffron, who returned six years later with the crew of Serenity to steal the Lassiter which he had acquired during the war in the above mannor. During this incident he walks in on the theft in progress and it becomes apparent that as soon as he saw her he called the feds, proving that is no fool.