Pell Underhill was a Human scientist native to Alpha Centauri.

In 2155, Underhill worked with Skon and Tobin Dax on Earth's warp seven program. (ENT - The Romulan War novel: Beneath the Raptor's Wing)

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Spoiler warning: Plot and/or ending details follow.

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In 2157, Underhill, Dax, and Skon were present at a failed test of countermeasures to the Romulan remote-hijack system. Underhill and Dax participated in a successful test later that day after Skon had been removed for being a security risk. (ENT - The Romulan War novel: To Brave the Storm)