Well it makes sense though. Think of it like this: Kid/Serge break into Viper Manor while Norris is undercover in the kitchen. A bru-haha breaks out upstairs and Kid gets poisoned. Word probably spreads throughout the manor that thieves snuck in but Lynx managed to fight them off. Norris, being a special agent in the military, probably had to prepare for any circumstances. He probably had some of that humour in his first-aid kit since he WAS in an area where that type of tactic (hydra poisoning) was used. He may have been attacked in a similar manner if his cover was blown so it makes sense he would have an antidote ready. So he hears the girl needs it and decides to be a nice guy and save her since he has what she needs. I like Norris =)