Zed
Explanation
This comic plays on the trope of dramatic romantic confrontations. A woman approaches a man and says "I need you to have sex with me," to which he objects "but you're married." She confirms that yes, she loves her husband, "and I love him more and more each day."
The final panel cuts to a conference setting with a banner, where a presenter explains: "There exists a number such that for every positive epsilon, the absolute value of [love] minus L is less than epsilon. That number is zed."
The punchline is a math joke about limits and convergence. In calculus, a sequence converges to a limit L if for every epsilon > 0, the terms eventually stay within epsilon of L. The woman's love for her husband is increasing but converging to a finite limit -- it will never actually reach infinity. "Zed" (the British/Commonwealth pronunciation of the letter Z) is the name of the man she's propositioning. The joke is that her love is bounded and converging, so while she does love her husband "more and more each day," the total is approaching a finite limit, leaving room for Zed. It's a clever use of mathematical analysis to justify infidelity through the technicality that an increasing sequence doesn't have to be unbounded.