Lizzy exactly four times, including this one, since riding off with Mr. Wickham to Newcastle nearly one year ago. Lizzy had written a dozen times, considered it her duty to do so, but in all honesty did not exalt in her sister's responses. Aside from the fact that she and her flighty youngest sister had never been tremendously akin, there was the uncomfortable reality of Lydia's marriage and current living situation that drove a deeper wedge between them. Lydia's letters were typical of her personality: self-centered, erratic, and unintelligent. Top that with incessant references to "my dear Wickham" and Lizzy was nauseous and headachy each time.
To make matters worse, it was the only area of her life she did not share with Darcy. He knew that she wrote to Lydia and was aware that she received the occasional reply; however, he never asked for details. He wished no ill upon Lydia in her marriage. Rather he harbored extreme guilt over the arrangement, knowing it was his involvement that shackled her to Wickham, even though there was no alternative as she had flatly refused to leave her "sweet Wickham's" side.
Darcy told Lizzy, much later, that his original plan was to use all the considerable means at his disposal to hush the scandal and restore Lydia to her family. Wickham was perfectly amenable to taking the money Darcy offered and disappearing, but Lydia refused to leave. He could not very well drag her away kicking and screaming, although it had crossed his mind, but then the scandal would be far more difficult to smother.
Furthermore, it had not taken Wickham long after his initial shock at seeing Darcy materialize with Lydia's Uncle Gardiner to realize Darcy's involvement in the situation was attributed to an attachment to Lizzy Bennet. The two men had known each other for too many years. Wickham uncannily deciphered the puzzle no matter how bland and uncommunicative Darcy attempted to be. Therefore Darcy had been forced to increase the sum offered Wickham in order to secure him marrying her, a step Wickham patently had no previous intention of taking. Even then, Darcy had worried that he would not follow through while simultaneously praying that he would run away and save Lydia the sad fate of being his wife.
During Lizzy and Darcy's engagement the topic had come up only once in a rebuttal to Mrs. Bennet discussing the guest list. Darcy bluntly stated that under no circumstance was Wickham to be invited to the wedding. Mrs. Bennet had moaned and dithered, muttering uncharitable comments about Mr. Darcy's character until Lizzy nearly snapped, saved only by her father steering her mother out of the room for a stern lashing. It was awful, increasingly so by the intense distress and anger of Darcy. Of course, the whole episode was unnecessary as Lydia was far too involved in her own affairs to bother traveling the distance to her sister's wedding, nor would Wickham have endured Darcy's ire.
Upon the receipt of Lydia's first correspondence after Lizzy's marriage, a full one month after in fact, Lizzy finally heard the entire story of Darcy's search for Wickham and Lydia. Her husband's lingering pain over the situation, remorse for being unable to rescue Lydia, and hatred toward Wickham was profound. Reliving the episode was tortuous, augmented by a residual grief due to his belief at the time that Elizabeth was beyond his reach. The last pieces of the mystery were revealed. They hugged, kissed, and made love, then vowed to never speak of it again.
It was not that Darcy refused to utter Wickham's or Lydia's name or hear them spoken in his presence; he merely preferred to avoid the topic. Therefore, Lizzy chose to facilitate tranquility and impede any suffering touching her husband by hiding the letters received and never mentioning her sister. Fortunately it was not a difficult chore, but she still hated anything remotely secretive between her and her spouse.
"Quit stalling, Lizzy," she chided herself, opening the letter