After ten months without a break, T'Pol notes efficiency onboard Enterprise is down three percent, and suggests a shore leave on the nearby tropical planet of Risa. Archer and Trip agree wholeheartedly and lay in a course to the exotic paradise. However, en route Archer receives a transmission from Admiral Forrest, informing him of a Vulcan Ambassador in need of immediate extradition from the nearby planet of Mazar. The matter is of some urgency, and with the closest Vulcan vessel over a week away Enterprise is to retrieve the Ambassador and deliver her to the Vulcan ship Sh'Raan at a rendezvous point in three days time.
Grudgingly belaying the crew's shore leave, Archer orders Mayweather to lay in a course for Mazar. After Hoshi donates her cabin for the Ambassador's use, T'Pol meticulously prepares the room and crew as to proper protocol in addressing the distinguished dignitary. Despite denying it to Archer, T'Pol is obviously highly anticipating the arrival of Ambassador V'Lar.
Arriving at Mazar, the ship is immediately hailed by a Mazarite Official, who informs Archer there is no need to send a shuttlepod to retrieve the Ambassador, as she is already on her way up. Curious at the extreme urgency of the Mazarites to be rid of the Ambassador, Archer and T'Pol are surprised to hear V'Lar has been expelled for abuse of her position and criminal misconduct. The Mazarite Official will give no further details, and abruptly ends the transmission.
Greeting V'Lar in the shuttle bay, Archer and T'Pol are taken aback at how cordial and friendly the Vulcan dignitary is: actually extending her hand to shake with the Captain and Trip; preferring to speak in English with T'Pol; and wishing to personally meet Hoshi to thank her for the use of her quarters. Over dinner at the Captain's table, V'Lar displays a disarming charm and grace, which she effectively uses to handle T'Pol's somewhat abrupt questions regarding how she intends to defend herself against the criminal charges. To T'Pol's shock V'Lar simply states she doesn't intend to defend herself, as there is no defense to use, and then excuses herself to retire for the evening. T'Pol escorts V'Lar to her temporary quarters for her stay, and there is a discernable tension between the two. T'Pol obviously believes V'Lar to be guilty of whatever crimes she is accused of, as she admitted there is no defense, conduct which is unheard of for a Vulcan Ambassador.
Archer intercepts T'Pol in the hall and addresses her behavior over dinner, but learns T'Pol actually met V'Lar years earlier, and the Ambassador had a profound influence on her life. Archer slowly understands what has been bothering his Science Officer: she is disappointed at her hero's sudden fall from grace. Interrupted from their talk, Archer is called to the bridge to address an unidentified approaching vessel. Answering the ship's hail, Archer speaks to a cordial Mazarite Captain who apologizes for the inconvenience, but it seems the Ambassador left too early and is to be returned to Mazar for further questioning, which he would be glad to do for Enterprise.
Sensing something awry of the Mazarite Captain, Archer stalls and asks for time to contact his superiors, then ends the transmission. Without warning, the Mazarite ship opens fire! Reed works furiously, but the torpedoes have no effect. Dropping out of warp, he fires the pulse cannons and disables the Mazarite ship's engines, leaving Enterprise clear to resume its course. Confronting V'Lar to get some answers, a fuming Archer finds the Ambassador regretfully unable to reveal the truth of her circumstances. Equally regretful, Archer has no choice but to act in the best interests of his crew's safety, and orders Mayweather to set a course to return to Mazar in order to drop the Ambassador off back with the Mazarites. En route, Archer again speaks to Admiral Forrest, who supports Archer's decision, but warns there may be repercussions for his actions.
Meanwhile, T'Pol finds V'Lar in the Mess Hall and joins her. The two discuss several things, including Archer's trustworthiness, and V'Lar recalls meeting T'Pol years ago, noting she was just as presumptuous and blunt then as she is now. Later, T'Pol informs Archer that V'Lar confided in her enough to know they must not return her to the Mazarites, or she will be killed. Despite being unable to learn anything more, T'Pol uncharacteristically displays passion in asking Archer to risk the crew's safety for the Ambassador by continuing to rendezvous with the Sh'Raan.
Trusting his instincts and seeing T'Pol's commitment to her words, Archer agrees and resumes his intercept course with the Vulcan ship. Nearly immediately, Enterprise comes under attack from three Mazarite ships. Outnumbered, Archer opts for flight and pushes Enterprise to her limits in a race to stay out of the Mazarite's weapons range long enough to rendezvous with the Sh'Raan. With the engines straining at warp four-point-five, Trip is unsure how long they will be able to hold their speed, much to Archer's chagrin as the Mazarite ships are all still steadily gaining on Enterprise.
Ambassador V'Lar suddenly asks to speak with Archer in the privacy of his ready room, and confesses the truth of her mission: she was to infiltrate the Mazarite government and gather evidence against corrupt officials, then testify against them in three months time. Her reputation was intentionally sullied with false allegations in an attempt to make the Mazarites believe she would no longer be a credible witness, thus leaving her alone long enough to testify.
Seeing that Enterprise cannot outrun the Mazarite ships, V'Lar wishes for Archer to drop out of warp so she may surrender herself for their safety. Finally understanding the importance of V'Lar to the Vulcan and Mazarite governments, Archer refuses to give up the fight until the very end, and resolves to push the ship to its limits in order to save V'Lar's life. Mayweather informs Archer the Mazarite engines are also overheating in the strain to keep up the grueling pace, but they're continuing to close in on Enterprise. With no choice, Archer orders a reluctant Trip to push it all the way to warp five.
Enterprise trembles from the strain, but the Mazarite vessels continue to gain. Sending a message to the Sh'Raan to meet Enterprise at maximum warp or it will be too late, Hoshi estimates the Vulcan ship should arrive within twelve minutes. Reluctantly realizing he has no choice but to drop out of warp or explode from the strain, Archer sends V'Lar to Sickbay. Stalling for time, Archer informs the Mazarite Captain that thanks to their weapons fire, Ambassador V'Lar suffered extensive plasma burns and is in critical condition.
Allowing the Mazarites to board Enterprise and go to Sickbay to see for themselves, where Dr. Phlox gives a surprisingly impassioned performance to save the life of his patient. The Mazarite visitors are unmoved, and fire their weapons into the chamber they believe is holding V'Lar in stasis. The Vulcan ship Sh'Raan arrives and threatens to destroy the Mazarite ships unless they surrender their weapons immediately, which they do. At this point, V'Lar appears and Archer's ruse is exposed. Rescued at the last minute, V'Lar is seen off the ship by Archer and T'Pol. With no more secrets between them, the three are finally able to fully appreciate the gravity of their sacrifices for each other, and a grateful V'Lar departs to continue her mission.