S7, E6: Kara (recurring guest star LAURA VANDERVOORT) travels to Washington to search for the crystal, but she is captured while breaking into a laboratory and sedated with a Kryptonite-infused truth serum. The dose causes her to relive a prior trip to Earth when she followed Clark's biological mother, Lara (recurring guest star HELEN SLATER - "Supergirl"), to the Kent farm. Clark arrives in time to save Kara but, after searing the machine with heat vision, he also falls victim to the serum and sees his mother through Kara's memories.