Sydnor also performs valuable undercover work, making hand-to-hand buys to build evidence, alongside Kima Greggs and her informant Bubbles.

Sydnor's initial attempt to disguise himself as a "junkie" is not credible to Bubbles, but he proves responsible for identifying Avon Barksdale at the annual West-Side versus East-Side basketball game.

When the money trail leads the investigation to major political figures, Sydnor worries about the potential damage to his career; nonetheless, he personally delivers the subpoena for financial records to State Senator Clay Davis.

When budget cuts in the department eventually lead to the unit being closed down, Sydnor is disappointed to find his work wasted and realizes that simply keeping Marlo under surveillance was effective in reducing crime.

The detectives present the evidence to State's Attorney Rupert Bond and he refuses to take the case federal as he wants to prosecute Davis himself for political reasons.

[9] In the series finale, Sydnor visits Judge Daniel Phelan in his chambers to apply back-channel pressure in order to advance an investigation, much like McNulty did in Season 1.