March 4, although B-unit shoots continued on March 8, with McNeil directing once more. This was in addition to further B-unit filming under the direction of Dan Curry for the episode "E²" and the start of the work on the season finale, "Zero Hour" under Allan Kroeker. Several elements of the props and effects were re-used from previous episodes. The reactor core on the superweapon was a combination of the props previously used as a Romulan mine in "Minefield" and rings from the Enterprise gymnasium which had appeared in the episode "Vanishing Point". The special effect used for the subspace vortexes created by the Sphere Builders had originally been created for the transwarp effect in the Voyager episode "Hope and Fear". The guest stars in "Countdown" were recurring from previous episodes, although it would be the final appearance for Steven Culp as Major Hayes. Culp had appeared in the series throughout the third season since "The Xindi". During the development of "The Shipment", Culp proposed the backstory for Hayes, which was accepted by the production team. The role was not his first in the Star Trek franchise, as he had been cast and filmed for an appearance as Commander Martin Madden for the film Star Trek: Nemesis. It would have seen him as the replacement for Commander William Riker at the end of the film, but it was cut from the final version. Reception "Countdown" was first aired in the United States on UPN on May 19, 2004. According to Nielsen Media Research, it received a 2.3/4 percent share among adults. This means that it was seen by 2.3 percent of all households, and 4 percent of all of those watching television at the time of the broadcast. The episode was watched by 3.5 million viewers. The following episode, "Zero Hour", received a 2.7/4 percent rating with the viewer number increased by 400,000. Michelle Erica Green, in her review for TrekNation, said that she saw the Hayes/Reed arc come full circle with the death of Hayes and the return of Reed to the position he had previously held prior to the MACO's arrival. She felt that otherwise, the episode consisted of action to the exclusion of character development but Green criticised the ease at which some of the Xindi side with Archer. She called it a "strong arc episode" and set-up the finale, but was concerned that the strong build-up