The Wings of a Butterfly ( audio story ) The Wings of a Butterfly was a 2010 audio short story written and performed by Colin Baker for Big Finish . It featured a companion - less Sixth Doctor . Written about the year 2000 , and previously published in the unlicensed anthology , " Missing Pieces " , the story explored the Doctor ' s willingness to change the flow of time in ways not authorised by the High Council of the Time Lord s . Summary . Visiting Gallifrey to attend an academic conference , the Sixth Doctor ' s old friend and mentor , Duotheros , requests that he use the TARDIS to examine a temporal anomaly centred on Bixor . The planet , once thriving , appears to have mysteriously eradicated itself , substantially reducing the number of people interested in buying Duotheros ' definitive history of that sector of space . Will the Doctor ' s investigations reveal the cause ? Or does Bixor ' s untimely demise have something to do with a certain blue box ? Plot . After giving a presentation at the Time Lord Academy , Duotheros invites his former student , the Doctor , to his study quarters to ask him a favour . Duotheros had been studying the history of the planet Bixor , when it was suddenly destroyed by an unknown event on the planet . As the Doctor was less inclined to ignore the mystery of the planet ' s destruction , compared to other Time Lords , Duotheros had decided to ask the Doctor to head to Bixor to discover the cause of its destruction . The Doctor agrees to the request and departs . Duotheros thinks about what he has just done , and , considering the Doctor ' s tendency to get involved with things he shouldn ' t , quickly changes his mind , heading to the door to call the Doctor back . Upon opening the door , he finds out he is too late , for standing outside the door is the Doctor , having just returned from Bixor . The two step back into the study . The Doctor explains what happened to Bixor . Its destruction was caused by a incorrectly made pair of trousers . A man had been wearing the trousers while walking on a crowded street , when the trousers fell down . People noticed and stopped to laugh at him . While they were all distracted , a pickpocket stole keys from the pocket of one of the laughing people . Upon discovering the car the keys belonged to , the pickpocket gave his bicycle to a nearby boy , before driving off in the stolen car . The boy , not used to riding a bicycle , was unsteady on it , and accidentally rode it out into the road , into the path of a large truck . The truck swerved to avoid the boy , accidentally crashing into a substation , causing a power outage to an entire manufacturing sector . It took hours for the damage to be repaired . One of the facilities affected was a vector module assembly plant . When the power was restored , the machinery in the factory sprung back to life , implanting sixteen modules with double printed circuits , which were subsequently installed into the guidance system of an aerial transport drone . The drone ' s function was to transport dangerous materials to the capital ' s central nuclear power generation plant . The drone ' s main system developed a fault , leading to the activation of the backup , double printed modules . When this occurred , the drone was flying over Bixor ' s only active volcanic fissure . The drone accelerated to sub - light speed and dove into the fissure . The dangerous materials reacted with the planet ' s magma , causing a chain reaction that destroyed Bixor . Duotheros is shocked upon hearing this . For Bixor , a world whose inhabitants were supposed to create great things , to be wiped out thanks to a pair of trousers is horrific . The Doctor offers to travel back to Bixor to make a " trouser adjustment " . As the destruction of Bixor has only just been discovered , the record of the event hasn ' t be uploaded to the Matrix yet , so the Time Lords won ' t know of him making such a change . Duotheros thinks about it and decides to take the risk . Upon returning to Bixor , the Doctor discovers why the trousers were incorrectly made , and swears to never do a favour for any old friends ever again . The trousers had been incorrectly made , because the worker who created the trousers had been distracted by a sight outside her window , the sight of the Doctor ' s TARDIS materialising outside the building . She had witnessed the Doctor ' s original arrival to Bixor , and it had been the Doctor ' s arrival to discover the cause of Bixor ' s destruction that had actually been the cause of its destruction . Knowing this , the Doctor travels back in time 30 years before his original arrival . He then plants a tree outside the building , one that would grow and block the window , preventing the worker from being distracted by his arrival resulting in the trousers being correctly made , averting the destruction of Bixor . The Doctor heads back to the TARDIS , only to discover something horrible . He had parked the TARDIS near another manufacturing plant , and multiple workers were staring out of their windows at him , meaning his second arrival had also been witnessed and had distracted some workers . The Doctor knows he can ' t risk that this event could once more lead to Bixor ' s destruction , so he decides to take no chances . He travels back in time one day , in the middle of the night , away from any building . He then walks back to the site of his second arrival and sets up a series of mirrors to obscure the spot where the TARDIS will appear , preventing the workers from seeing his arrival . Upon finishing , the Doctor returns to the TARDIS and departs , heading back to Gallifrey . Upon arriving , he is greeted by Duotheros , who has no recollection of the timeline in which Bixor was destroyed , or of having met with the Doctor anytime recently .