[1] Showrunner Krista Vernoff discussed the challenge in writing Alex off without Chambers physically being there, having left the show suddenly.

She re-appears for the first time again through extensive use of archive footage as well as visual cameos portrayed by a body double, as details of her current situation are revealed, along with Chambers' character.

The episode's original broadcast was watched by 6.30 million viewers and registered the show's best ratings in 6 weeks, since the mid-season premiere.

It received polarized reviews from fans and critics alike, who were divided on the show's handling of Alex's exit, but many largely felt it made sense given the circumstances of Chambers' abrupt departure.

It features Meredith Grey (Ellen Pompeo), Cristina Yang (Sandra Oh), Izzie Stevens (Katherine Heigl), Alex Karev (Justin Chambers) and George O'Malley (T. R. Knight).

The episode then provides a retrospective of landmark storylines in the series integral to Alex's whole journey, from his arrogant, smart-mouth days in the early seasons to his maturation as a successful pediatrics surgeon, devoted friend and partner to Izzie and later Jo.

Alex reveals Izzie was single, wanted kids and because the cancer nuked her eggs, she could not have biological children but she had their embryos.

Meanwhile, Jo swallows her emotions and decides to continue to work casually after reading the letter as Link (Chris Carmack) calls her his hero.

Several former characters appear in the episode through archive footage such as Izzie Stevens (Katherine Heigl), Denny Duquette (Jeffrey Dean Morgan), George O'Malley (T. R. Knight), Cristina Yang (Sandra Oh), Derek Shepherd (Patrick Dempsey), Shane Ross (Gaius Charles), Stephanie Edwards (Jerrika Hinton), Arizona Robbins (Jessica Capshaw), Helen Karev (Lindsay Wagner) and Jimmy Evans (James Remar).

The only current main cast members that appeared in new scenes were Meredith Grey (Ellen Pompeo), Miranda Bailey (Chandra Wilson), Richard Webber (James Pickens Jr.), Jo Karev (Camilla Luddington) and Atticus "Link" Lincoln (Chris Carmack).

Alex and Izzie's storyline was left unresolved in the sixth season, after Heigl departed the series abruptly during her maternity leave.

Heigl's 3-month family leave in Utah propelled her to quit the show entirely, feeling she needed more time to bond with her adoptive daughter.

[4] In August 2010, Rhimes stated that she did not feel Alex and Izzie's arc had fully concluded, and hoped to give proper closure to their relationship in the seventh season.

[5] She later confirmed that she had intended to kill off Izzie off-screen, but opted against this a day later as she felt that it would destroy Alex, rather than give him closure.

“There was no way to not put those characters through gut-wrenching, ongoing grief if we had killed Alex off camera.” She also felt the second option would have done a disservice to Camilla Luddington who plays Chambers' TV wife.

“It would absolutely eliminate [the chance for her to play] so many colors that she is so good at playing” and finally evaluated as a result that it “...wasn’t even a debate in the writers room,” adding that giving Alex a happy ending with Izzie “was so clearly the right course.”[12] Debbie Allen who directed the episode “fought really hard to cast and shoot the kids” according to Vernoff, explaining that it was not in the original script.

[14] "Leave the Light On" received polarized reviews from television critics and fans alike, who were divided on the show's handling of Alex's exit, but many largely felt it made sense given the circumstances of Chambers' abrupt departure.

USA Today noted that the episode was "polarizing" to fans, and on discussing Alex's whole journey said, "He was there for us as we watched a succession of doctors depart the series.

Then again: Maybe Izzie was that stability all along..."[15] Deadline noted "fan-favorite" Alex's ending's similarities to that of ER's Doug and Carol, played by George Clooney and Julianna Margulies respectively, "who also left the show at different times" and there "Carol also had given birth to the couple’s twins unbeknownst to Doug, with the couple eventually reuniting to live happily ever after with their kids".

[16] In a 3-out-of-5-star review, Maggie Fremont for Vulture expressed disappointment that the "clip-show" exit showed no physical reunion between Izzie and Alex.

"[18] Sonya Field for Hypable criticized the "unrealistic" storyline, feeling that it underscored Alex and Jo's story "because he was so ready to leave her".

Blu also criticized Alex for seemingly using his sick mother as an alibi, and noted it as being uncharacteristic of the "straight-shooter" and "guy who tells it like it is whether you like it or not" that fans know him by.

The reviewer also noted that it was "already a disservice that it took so long for anyone to pay attention to his absence" and that "Jo probably should've contacted his mother ages ago".