Best-laid plan, bar the laid part

Season 1 or 2: Eager to socially move upwards, Thomas has made up a wonderful plan: charm one of his employer's youngest daughters, marry her and become Lord Grantham's son-in-law. What a social climbing! But there's still a few things in the way. Like his total lack of attraction and desire for women, for instance. One-shot. Written for January 2014's "Downton monthly prompt".