The story of Marvell's conversion is emphatic but vague in its details. The "Jesuits," who were well represented in Cambridge at the time, are said to have persuaded him to leave Cambridge secretly, and to take refuge in one of their houses in London. Thither the elder Marvell followed in pursuit, and after search came across his son in a bookseller's shop, where he succeeded both in convincing the boy of his errors and in persuading him to return to Trinity. An odd story, and not, as it stands, very credible; but Mr. Grosart discovered among the Marvell papers at Hull a fragment of a letter without signature, address, or date, which throws some sort of light on the incident. This letter was evidently, as Mr. Grosart surmises, sent to the elder Marvell by some similarly afflicted parent. In its fragmentary state the letter reads as follows:-- "Worthy S^r,--M^r Breerecliffe being w^th me to-day, I related vnto him a fearfull passage lately at Cambridg touching a sonne of mine, Bachelor of Arts in Katherine Hall, w^ch was this. He was lately inuited to a supper in towne by a gentlewoman, where was one M^r Nichols a felow of Peterhouse, and another or two masters of arts, I know not directly whether felowes or not: my sonne hauing noe p'ferment, but liuing meerely of my penny, they pressed him much to come to liue at their house, and for chamber and extraordinary bookes they promised farre: and then earnestly moued him to goe to Somerset house, where they could doe much for p'ferring him to some eminent place, and in conclusion to popish arguments to seduce him soe rotten and vnsauory as being ouerheard it was brought in question before the heads of the Uniuersity: _Dr. Cosens_, being _Vice Chancelor_ noe punishment is inioined him: but on Ash-wednesday next a recantation in regent house of some popish tenets Nicols let fall: I p'ceive by M^r Breercliffe some such prank vsed towards y^r sonne: I desire to know what y^u did therin: thinking I cannot doe god better seruice then bring it vppon the stage either in Parliament if it hold: or informing some Lords of the Counsail to whom I stand much oblieged if a bill in Starchamber be meete To terrify others by making these some publique spectacle: for if such fearfull practises may goe vnpunished I take care whether I may send a child ... the lord."[15:1] The reference to Dr. Cosens, or Cosin, being Vice-Chancellor gives a clue to the date, for Cosin was chosen Vice-Chancellor on the 4th of November 1639.[15:2]