House discovers that the sisters were all taking a specific "natural" performance-enhancing supplement to stay thin for gymnastics. Because of a rare phenomenon in female development (skewed X-inactivation), each sister's body processed the supplement's toxins differently:
The breakthrough comes when Chloe, the "healthy" one, finally collapses. House realizes the common denominator isn't what they are doing , but what they are taking . The Diagnosis: Dr. House: 2Г—3
liver couldn't break down the heavy metals, leading to pulmonary edema. Lea's neurological system took the hit, causing seizures. House discovers that the sisters were all taking
House orders an aggressive chelation therapy tailored to each sister's specific organ failure. As they recover, the sisters realize that their drive for "identical perfection" nearly killed them. The episode ends with House alone in his office, spinning a juggling ball—reflecting on how even "identical" things are never truly the same. The Diagnosis: liver couldn't break down the heavy
: House treats them as a single organism with three different "outputs." He theorizes that while their DNA is the same, their epigenetics —how those genes are expressed—have diverged due to secret lifestyle differences.