NorthWest Biotherapeutics Inc (NWBO)

[flyfishingcherokee]

Closing gap action is a result of the MM who is required to deliver stock that they may not own to the buyer who buys at the gap price. The MM will then cover that delivery of stock that was "borrowed" (all legal if you are a MM) by driving the price back down to a level that produces a profit to the MM as he/she covers the borrowed shares. i.e. sell high and buy low.
MM are legally allowed to manufacture this profit as an offset for the risk they take in providing a market at any price (except in the case of a "flash drop" in the market at which point even a MM will refuse to provide market liquidity).
There are examples when the buying volume is so strong that the MM is unable to drop the price back down for an extended period of trading days but eventually the buying strength weakens for the stock and then the price is made to drop down to a level that the MM can cover at a profitable level, resulting in "closing the gap". Afterward the stock may see renewed buying again because of the lower prices and a rebound to higher prices may result. (The resumption of the "trend")