Arrow Barry Allen (Grant Gustin, left) and Oliver Queen (Stephen Amell) will come together in "The Flash"-"Arrow" crossover episodes on Dec. 2 and Dec. 3. Photo: The CW

Fans have just about a week to go before “The Flash” and “Arrow” crossover fun begins. The CW two-part event, taking place on Dec. 2 and Dec. 3 at the regular 8 p.m. EST time slots, will feature all sorts of twists and turns as the two worlds come together. The Hollywood Reporter got the scoop on how Team Arrow and S.T.A.R. Labs will both help and hurt each other in the crossover special, perhaps even answering one of “Arrow” fans’ biggest questions.

S.T.A.R. Labs will helping out big time. According to the Hollywood Reporter, the Dr. Wells (Tom Cavanagh) and his team will be using their skills and technology to help their Starling City friends solve a big mystery -- who killed Sara Lance (Caity Lotz) aka the Black Canary. Lance was killed in the “Arrow” Season 3 premiere after helping Oliver (Stephen Amell) take down Count Vertigo (Peter Stormare). The producers have previously promised that the character will return at least three times via flashbacks. Will one of those come in the crossover?

While S.T.A.R. Labs appear to be helping out Team Arrow, the Flash (Grant Gustin) might be giving Oliver Queen some problems. The first episode of the crossover, episode 8 of “The Flash,” will pit the two superheroes against each other. Apparently, a new meta-human will enter the fray and, after facing off with Barry, he will have a strange effect on the Central City hero. Will that meta-human be one of the announced villains for the episode --Captain Boomerang or the Weather Wizard? Whoever it is, he will brainwash the Flash, who will be acting so crazy that he turns on Oliver. Though the two will go head-to-head, Oliver, who showed up in the "Flash” pilot to give Barry advice, will only be trying to set his friend straight.

Will Oliver be able to help Barry? Will S.T.A.R. Labs solve the Black Canary murder? Fans will get the answers to their questions in a week. The "Flash” and “Arrow” crossover begins Dec. 2 at 8 p.m. EST and continues Dec. 3 at 8 p.m. EST on the CW.

Who do you think killed Sara Lance? Tweet your thoughts to @Ja9GarofaloTV