Joe Orlando joins Haney and Paris on Metamorpho 5 (March/April 1966), and does a very good job maintaining the look and feel of the series.
The story deals with a crackpot inventor, Edifice K. Bulwark, who gets Simon Stagg interested in constructing his chemical skyscrapers. Metamorpho would be needed to build them, but the hero refuses, as other scientists, and even the media, are sure the buildings would be deadly disasters.
Stagg pulls out the Orb of Ra, which hasn't been seen since this series began. Credited with turning Rex Mason into Metamorpho, Stagg uses it to transform Bulkwark into a second element man.
Even Sapphire Stagg cannot tell the two men apart, and Bulwark uses his powers to build his changeable chemical skyscraper. It begins to malfunction immediately, and though Bulwark is able to use his powers to save Stagg, Sapphire and Java from an elevator crash, the real Metamorpho winds up going into action when the skyscraper begins attacking other buildings.
Bulwark wants to defend his structure, so it becomes a battle between the element men. Metamorpho defeats Bulwark, and then destroys the dangerous skyscraper. Stagg's process for transforming Bulwark turns out to be temporary, and he returns to human form at the end of the story.