 At Torchwood 's Cardiff headquarters , Owen determines from an autopsy that the alien that impregnated Gwen is a Nostrovite , a race of carnivorous shape <unk> who hunt in pairs and mate for life . He tells Jack that after fertilisation , the female transfers her eggs to the male who plants them in a host body until they are ready to hatch . Later , the female kills the host to release the offspring . At the wedding venue , the female Nostrovite ( <unk> Brown ) murders and partly <unk> wedding guest Mervyn . Toshiko investigates along with Rhys ' best man " Banana Boat " ( Jonathan Lewis Owen ) and they are subsequently captured by the alien , who intends to feed on them later . As Gwen and Rhys prepare to say their wedding vows , Jack runs up the aisle and demands that the wedding be halted . Owen and <unk> ( Gareth David @-@ Lloyd ) free Toshiko but the half @-@ eaten corpse of Mervyn is discovered by his wife , a <unk> , who alerts the entire wedding party to the murder . The Nostrovite reveals herself and is chased away by Jack , escaping through a window . 
